Accelerants for additive manufacturing with dual cure resins

ABSTRACT

A method of forming a three-dimensional object is provided herein, which may be carried out by: (a) providing a carrier and a fill level, the carrier and the fill level having a build region therebetween; (b) filling the build region with a polymerizable liquid, the polymerizable liquid comprising a mixture of (i) a light polymerizable liquid first component, and (ii) a second solidifiable component that is different from the first component; the polymerizable liquid further comprising a Lewis acid or an oxidizable tin salt in an amount effective to accelerate the formation of the three-dimensional intermediate during the irradiating; and (c) irradiating the build region with light to form a solid polymer scaffold from the first component and also advancing the carrier away from the build surface to form a three-dimensional intermediate.

RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 national phase entry of PCTApplication PCT/US2016/066560, filed Dec. 14, 2016, and published inEnglish on Jun. 29, 2017, as International Publication No. WO2017/112483, and which claims the benefit of U.S. Provisional PatentApplication No. 62/270,702, filed Dec. 22, 2015, the disclosure of eachof which is incorporated herein by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention concerns materials, methods and apparatus for thefabrication of solid three-dimensional objects from liquid materials,and objects so produced.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object.

If new layers are formed at the top surface of the growing object, thenafter each irradiation step the object under construction is loweredinto the resin “pool,” a new layer of resin is coated on top, and a newirradiation step takes place. An early example of such a technique isgiven in Hull, U.S. Pat. No. 5,236,637, at FIG. 3. A disadvantage ofsuch “top-down” techniques is the need to submerge the growing object ina (potentially deep) pool of liquid resin and reconstitute a preciseoverlayer of liquid resin.

If new layers are formed at the bottom of the growing object, then aftereach irradiation step the object under construction must be separatedfrom the bottom plate in the fabrication well. An early example of sucha technique is given in Hull, U.S. Pat. No. 5,236,637, at FIG. 4. Whilesuch “bottom-up” techniques hold the potential to eliminate the need fora deep well in which the object is submerged by instead lifting theobject out of a relatively shallow well or pool, a problem with such“bottom-up” fabrication techniques, as commercially implemented, is thatextreme care must be taken, and additional mechanical elements employed,when separating the solidified layer from the bottom plate due tophysical and chemical interactions therebetween. For example, in U.S.Pat. No. 7,438,846, an elastic separation layer is used to achieve“non-destructive” separation of solidified material at the bottomconstruction plane. Other approaches, such as the B9Creator™3-dimensional printer marketed by B9Creations of Deadwood, S. Dak., USA,employ a sliding build plate. See, e.g., M. Joyce, US Patent App.2013/0292862 and Y. Chen et al., US Patent App. 2013/0295212 (both Nov.7, 2013); see also Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012). Such approaches introduce a mechanical stepthat may complicate the apparatus, slow the method, and/or potentiallydistort the end product.

Continuous processes for producing a three-dimensional object aresuggested at some length with respect to “top-down” techniques in U.S.Pat. No. 7,892,474, but this reference does not explain how they may beimplemented in “bottom-up” systems in a manner non-destructive to thearticle being produced, which limits the materials which can be used inthe process, and in turn limits the structural properties of the objectsso produced.

Southwell, Xu et al., US Patent Application Publication No.2012/0251841, describe liquid radiation curable resins for additivefabrication, but these comprise a cationic photoinitiator (and hence arelimited in the materials which may be used) and are suggested only forlayer by layer fabrication.

Velankar, Pazos, and Cooper, Journal of Applied Polymer Science 162,1361 (1996), describe UV-curable urethane acrylates formed by adeblocking chemistry, but they are not suggested for additivemanufacturing, and no suggestion is made on how those materials may beadapted to additive manufacturing.

Accordingly, there is a need for new materials and methods for producingthree-dimensional objects by additive manufacturing that havesatisfactory structural properties.

SUMMARY OF THE INVENTION

Described herein are methods, systems and apparatus (includingassociated control methods, systems and apparatus), for the productionof a three-dimensional object by additive manufacturing. In preferred(but not necessarily limiting) embodiments, the method is carried outcontinuously. In preferred (but not necessarily limiting) embodiments,the three-dimensional object is produced from a liquid interface. Hencethey are sometimes referred to, for convenience and not for purposes oflimitation, as “continuous liquid interface production,” “continuousliquid interphase printing,” or the like (i.e., “CLIP”). A schematicrepresentation of an embodiment thereof is given in FIG. 1 herein.

The present invention provides a method of forming a three-dimensionalobject, comprising: (a) (i) providing a carrier and an opticallytransparent member having a build surface, the carrier and the buildsurface defining a build region therebetween, or (ii) providing acarrier in a polymerizable liquid reservoir, the reservoir having a filllevel, the carrier and the fill level defining a build regiontherebetween; (b) filling the build region with a polymerizable liquid,the polymerizable liquid comprising a mixture of: (i) a lightpolymerizable liquid first component, and (ii) a second solidifiable (orsecond reactive) component different from the first component; (c)irradiating the build region with light (through the opticallytransparent member when present) to form a solid polymer scaffold fromthe first component and advancing (e.g., advancing concurrently—that is,simultaneously, or sequentially in an alternating fashion withirradiating steps) the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object and containing the secondsolidifiable component carried in the scaffold in unsolidified oruncured form; and (d) concurrently with or subsequent to the irradiatingstep, solidifying and/or curing (e.g., further reacting, polymerizing,or chain extending) the second solidifiable or reactive component in thethree-dimensional intermediate to form the three-dimensional object.

Optionally, a wash step may be included between formation of thethree-dimensional intermediate and the subsequent solidifying and/orcuring step (d) (which may then be step (e)) by which thethree-dimensional object is formed. Any suitable wash liquid may beemployed (e.g., BIO-SOLV™ solvent replacement; PURPLE POWER™degreaser/cleaner, SIMPLE GREEN® all purpose cleaner; a 50:50volume:volume mixture of water and isopropanol, etc. See also, U.S. Pat.No. 5,248,456).

In some embodiments, the second component comprises: (i) a polymerizableliquid solubilized in or suspended in the first component; (ii) apolymerizable solid solubilized in the first component; or (iii) apolymer solubilized in the first component. In other embodiments, thesecond component comprises: (i) a polymerizable solid suspended in thefirst component; or (ii) solid thermoplastic or thermoset polymerparticles suspended in the first component.

In some embodiments, the first component comprises a blocked or reactiveblocked prepolymer and (optionally but in some embodiments preferably) areactive diluent, and the second component comprises a chain extender.The first components react together to form a blocked polymer scaffoldduring the irradiating step, which is unblocked by heating or microwaveirradiating during the second step to, in turn, react with the chainextender. In some embodiments, the reactive blocked component comprisesa reactive blocked diisocyanate and/or chain extender, alone or incombination with a reactive blocked prepolymer, and other unblockedconstituents (e.g., polyisocyanate oligomer, diisocyanate, reactivediluents, and/or chain extender).

In some embodiments, reactive blocked prepolymers, diisocyanates, and/orchain extenders are blocked by reaction of (i.e., are the reactionproduct of a reaction between) a polyisocyanate oligomer, adiisocyanate, and/or a chain extender with an amine (meth)acrylate,alcohol (meth)acrylate, maleimide, or n-vinylformamide monomer blockingagent.

In some embodiments, the three-dimensional intermediate is collapsibleor compressible (e.g., elastic).

In some embodiments, the scaffold is continuous; in other embodiments,the scaffold is discontinuous (e.g., an open or closed cell foam, whichfoam may be regular (e.g., geometric, such as a lattice) or irregular).

In some embodiments, the three-dimensional object comprises a polymerblend (e.g., an interpenetrating polymer network, asemi-interpenetrating polymer network, a sequential interpenetratingpolymer network) formed from the first component and the secondcomponent.

In some embodiments, the polymerizable liquid comprises from 1, 2 or 5percent by weight to 20, 30, 40, 90 or 99 percent by weight of the firstcomponent; and from 1, 10, 60, 70 or 80 percent by weight to 95, 98 or99 percent by weight of the second component (optionally including oneor more additional components). In other embodiments, the polymerizableliquid comprises from 1, 2 or 5 percent by weight to 20, 30, 40, 90 or99 percent by weight of the second component; and from 1, 10, 60, 70 or80 percent by weight to 95, 98 or 99 percent by weight of the firstcomponent (optionally including one or more additional components).

In some embodiments, the solidifying and/or curing step (d) is carriedout concurrently with the irradiating step (c) and: (i) the solidifyingand/or curing step is carried out by precipitation; (ii) the irradiatingstep generates heat from the polymerization of the first component in anamount sufficient to thermally solidify or polymerize the secondcomponent (e.g., to a temperature of 50 or 80 to 100° C., forpolymerizing polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)); and (iii) the second component (e.g., a light orultraviolet light curable epoxy resin) is solidified by the same lightas is the first component in the irradiating step.

In some embodiments, the solidifying and/or curing step (d) is carriedout subsequent to the irradiating step (c) and is carried out by: (i)heating or microwave irradiating the second solidifiable component; (ii)irradiating the second solidifiable component with light at a wavelengthdifferent from that of the light in the irradiating step (c); (iii)contacting the second polymerizable component to water; or (iv)contacting the second polymerizable component to a catalyst.

In some embodiments, the second component comprises precursors to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), a silicone resin, or natural rubber, and thesolidifying and/or curing step is carried out by heating or microwaveirradiating.

In some embodiments, the second component comprises a cationically curedresin (e.g., an epoxy resin or a vinyl ether) and the solidifying and/orcuring step is carried out by irradiating the second solidifiablecomponent with light at a wavelength different from that of the light inthe irradiating step (c).

In some embodiments, the second component comprises a precursor to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), and the solidifying and/or curing step is carriedout by contacting the second component to water (e.g., in liquid, gas,or aerosol form). Suitable examples of such precursors include, but arenot limited to, those described in B. Baumbach, Silane TerminatedPolyurethanes (Bayer Material Science 2013).

In some embodiments, the second component comprises a precursor to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), a silicone resin, a ring-opening metathesispolymerization resin, or a click chemistry resin (alkyne monomers incombination with compound plus an azide monomers), and the solidifyingand/or curing step is carried out by contacting the second component toa polymerization catalyst (e.g., a metal catalyst such as a tincatalyst, and/or an amine catalyst, for polyurethane/polyurea resins;platinum or tin catalysts for silicone resins; ruthenium catalysts forring-opening metathesis polymerization resins; copper catalyst for clickchemistry resins; etc., which catalyst is contacted to the article as aliquid aerosol, by immersion, etc.), or an aminoplast containing resin,such as one containing N-(alkoxymethyl)acrylamide, hydroxyl groups, anda blocked acid catalyst.

In some embodiments, the irradiating step and/or advancing step iscarried out while also concurrently:

(i) continuously maintaining a dead zone (or persistent or stable liquidinterface) of polymerizable liquid in contact with the build surface,and

(ii) continuously maintaining a gradient of polymerization zone (e.g.,an active surface) between the dead zone and the solid polymer and incontact with each thereof, the gradient of polymerization zonecomprising the first component in partially cured form.

In some embodiments, the first component comprises a free radicalpolymerizable liquid and the inhibitor comprises oxygen; or the firstcomponent comprises an acid-catalyzed or cationically polymerizableliquid, and the inhibitor comprises a base.

In some embodiments, the gradient of polymerization zone and the deadzone together have a thickness of from 1 to 1000 microns.

In some embodiments, the gradient of polymerization zone is maintainedfor a time of at least 5, 10, 20 or 30 seconds, or at least 1 or 2minutes.

In some embodiments, the advancing is carried out at a cumulative rateof at least 0.1, 1, 10, 100 or 1000 microns per second.

In some embodiments, the build surface is substantially fixed orstationary in the lateral and/or vertical dimensions.

In some embodiments the method further comprises verticallyreciprocating the carrier with respect to the build surface to enhanceor speed the refilling of the build region with the polymerizableliquid.

A further aspect of the invention is a polymerizable liquidsubstantially as described herein above and below, and/or for use incarrying out a method as described herein.

In some embodiments of the methods and compositions described above andbelow, the polymerizable liquid (or “dual cure resin”) has a viscosityof 100, 200, 500 or 1,000 centipoise or more at room temperature and/orunder the operating conditions of the method, up to a viscosity of10,000, 20,000, or 50,000 centipoise or more, at room temperature and/orunder the operating conditions of the method.

One particular embodiment of the inventions disclosed herein is a methodof forming a three-dimensional object comprised of polyurethane,polyurea, or copolymer thereof, the method comprising: (a) providing acarrier and an optically transparent member having a build surface, thecarrier and the build surface defining a build region therebetween; (b)filling the build region with a polymerizable liquid, the polymerizableliquid comprising at least one of: (i) a blocked or reactive blockedprepolymer, (ii) a blocked or reactive blocked diisocyante, or (iii) ablocked or reactive blocked diisocyanate chain extender; (c) irradiatingthe build region with light through the optically transparent member toform a solid blocked polymer scaffold and advancing the carrier awayfrom the build surface to form a three-dimensional intermediate havingthe same shape as, or a shape to be imparted to, the three-dimensionalobject, with the intermediate containing the chain extender; and then(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form from the three-dimensional intermediate thethree-dimensional object comprised of polyurethane, polyurea, orcopolymer thereof.

In some embodiments, the solidifiable or polymerizable liquid is changedat least once during the method with a subsequent solidifiable orpolymerizable liquid; optionally where the subsequent solidifiable orpolymerizable liquid is cross-reactive with each previous solidifiableor polymerizable liquid during the subsequent curing, to form an objecthaving a plurality of structural segments covalently coupled to oneanother, each structural segment having different structural (e.g.,tensile) properties.

A further aspect of the inventions disclosed herein is a polymerizableliquid useful for the production of a three-dimensional object comprisedof polyurethane, polyurea, or a copolymer thereof by additivemanufacturing, the polymerizable liquid comprising a mixture of:

-   -   (a) at least one constitutent selected from the group consisting        of (i) a blocked or reactive blocked prepolymer, (ii) a blocked        or reactive blocked diisocyanate, and (iii) a blocked or        reactive blocked diisocyanate chain extender,    -   (b) optionally at least one additional chain extender,    -   (c) a photoinitiator,    -   (d) optionally a polyol and/or a polyamine,    -   (e) optionally a reactive diluent,    -   (f) optionally a non-reactive (i.e., non-reaction initiating)        light absorbing, particularly a ultraviolet light-absorbing,        pigment or dye which when present is included in an amount of        from 0.001 or 0.01 to 10 percent by weight, and    -   (g) optionally a filler (e.g., silica, a toughener such as a        core-shell rubber, etc., including combinations thereof);    -   optionally, but in some embodiments preferably, subject to the        proviso that the non-reactive light absorbing pigment or dye is        present when the at least one constituent is only the blocked or        reactive blocked prepolymer.

In some embodiments, polymerizable liquids used in the present inventioninclude a non-reactive pigment or dye. Examples include, but are notlimited to, (i) titanium dioxide (e.g., in an amount of from 0.05 or 0.1to 1 or 5 percent by weight), (ii) carbon black (e.g., included in anamount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) anorganic ultraviolet light absorber such as a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxypenyltriazine, and/or benzotriazole ultraviolet light absorber(e.g., in an amount of 0.001 or 0.005 to 1, 2 or 4 percent by weight).

In some embodiments, a Lewis acid or an oxidizable tin salt is includedin the polymerizable liquid (e.g., in an amount of from 0.01 or 0.1 to 1or 2 percent by weight, or more) in an amount effective to acceleratethe formation of the three-dimensional intermediate object during theproduction thereof.

A further aspect of the inventions disclosed herein is athree-dimensional object comprised of: (a) a light polymerized firstcomponent; and (b) a second solidified component (e.g., a furtherreacted, polymerized or chain extended component) different from thefirst component; optionally but in some embodiments preferably subjectto the proviso that: (i) the second component does not contain acationic polymerization photoinitiator, and/or (ii) thethree-dimensional object is produced by the process of continuous liquidinterface production.

In some embodiments, the object further comprises: (c) a thirdsolidified (or further reacted, polymerized, or chain extended)component different from the first and second component, with the objecthaving at least a first structural segment and a second structuralsegment covalently coupled to one another, the first structural segmentcomprised of the second solidified component, the second structuralsegment comprised of the third solidified component; and both the firstand second structural segments comprised of the same or different lightpolymerized first component.

In some embodiments, the object comprises a polymer blend formed fromthe first component and the second component.

The object may be one that has a shape that cannot be formed byinjection molding or casting.

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the drawings herein and thespecification set forth below. The disclosures of all United StatesPatent references cited herein are to be incorporated herein byreference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a method of thepresent invention.

FIG. 2 is a perspective view of one embodiment of an apparatus of thepresent invention.

FIG. 3 is a first flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 4 is a second flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 5 is a third flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 6 is a top view of a 3 inch by 16 inch “high aspect” rectangularbuild plate (or “window”) assembly of the present invention, where thefilm dimensions are 3.5 inch by 17 inch.

FIG. 7 is an exploded view of the build plate of FIG. 6, showing thetension ring and tension ring spring plate.

FIG. 8 is a side sectional view of the build plates of FIG. 6 and FIG.7, showing how the tension member tensions and rigidifies the polymerfilm.

FIG. 9 is a top view of a 2.88 inch diameter round build plate of theinvention, where the film dimension may be 4 inches in diameter.

FIG. 10 is an exploded view of the build plate of FIG. 9.

FIG. 11 shows various alternate embodiments of the build plates of FIG.6-FIG. 10.

FIG. 12 is a front perspective view of an apparatus according to anexemplary embodiment of the invention.

FIG. 13 is a side view of the apparatus of FIG. 12.

FIG. 14 is a rear perspective view of the apparatus of FIG. 12.

FIG. 15 is a perspective view of a light engine assembly used with theapparatus of FIG. 12.

FIG. 16 is a front perspective view of an apparatus according to anotherexemplary embodiment of the invention.

FIG. 17A is a schematic diagram illustrating tiled images.

FIG. 17B is a second schematic diagram illustrating tiled images.

FIG. 17C is a third schematic diagram illustrating tiled images.

FIG. 18 is a front perspective view of an apparatus according to anotherexemplary embodiment of the invention.

FIG. 19 is a side view of the apparatus of FIG. 18.

FIG. 20 is a perspective view of a light engine assembly used with theapparatus of FIG. 18.

FIG. 21 is a graphic illustration of a process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out continuously. Advancing of the carrier isillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 22 is a graphic illustration of another process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out stepwise, yet the dead zone and gradient ofpolymerization are maintained. Advancing of the carrier is againillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 23 is a graphic illustration of still another process of theinvention indicating the position of the carrier in relation to thebuild surface or plate, where both advancing of the carrier andirradiation of the build region is carried out stepwise, the dead zoneand gradient of polymerization are maintained, and a reciprocating stepis introduced between irradiation steps to enhance the flow ofpolymerizable liquid into the build region. Advancing of the carrier isagain illustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 24 is a detailed illustration of an reciprocation step of FIG. 23,showing a period of acceleration occurring during the upstroke (i.e., agradual start of the upstroke) and a period of deceleration occurringduring the downstroke (i.e., a gradual end to the downstroke).

FIG. 25A depicts a dual cure system employing a thermally cleavable endgroup. I. Crosslinked blocked diisocyanate prepolymer containingunreacted chain extender. II. Polymer blend of: i) linear ethylenicallyunsaturated blocking monomer copolymerized with reactive diluent and ii)linear thermoplastic polyurethane.

FIG. 25B depicts a method of the present invention carried out with(meth)acrylate blocked diisocyanates (ABDIs). I. Crosslinked blockeddiisocyanate containing unreacted soft segment and chain extender. II.Polymer blend of: i) linear ethylenically unsaturated blocking monomercopolymerized with reactive diluent and ii) linear thermoplasticpolyurethane.

FIG. 25C depicts a method of the present invention carried out with(meth)acrylate blocked chain extenders (ABCEs). I. Crosslinked blockeddiisocyanate containing chain extender containing unreacted soft segmentand chain extender. II. Polymer blend of: i) linear ethylenicallyunsaturated blocking monomer copolymerized with reactive diluent and ii)linear thermoplastic polyurethane.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Where used, broken lines illustrate optionalfeatures or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly-useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

“Shape to be imparted to” refers to the case where the shape of theintermediate object slightly changes between formation thereof andforming the subsequent three-dimensional product, typically by shrinkage(e.g., up to 1, 2 or 4 percent by volume), expansion (e.g., up to 1, 2or 4 percent by volume), removal of support structures, or byintervening forming steps (e.g., intentional bending, stretching,drilling, grinding, cutting, polishing, or other intentional formingafter formation of the intermediate product, but before formation of thesubsequent three-dimensional product). As noted above, thethree-dimensional intermediate may also be washed, if desired, beforefurther curing, and/or before, during, or after any intervening formingsteps.

“Hydrocarbyl” as used herein refers to a bifunctional hydrocarbon group,which hydrocarbon may be aliphatic, aromatic, or mixed aliphatic andaromatic, and optionally containing one or more (e.g., 1, 2, 3, or 4)heteroatoms (typically selected from N, O, and S). Such hydrocarbylgroups may be optionally substituted and may contain from 1, 2, or 3carbon atoms, up to 6, 8 or 10 carbon atoms or more, and up to 40, 80,or 100 carbon atoms or more.

“Hard-segment” and “soft-segment” as used herein derive from themorphology of elastomeric polymers which can contain distinct phaseseparated regions. Such regions can be detected by thermoanalysistechniques and distinguished by, for example, glass transitiontemperatures. Generally, soft-segments of the polymer can be consideredas having glass transition temperatures below room temperature whilsthard-segments can be considered as having glass transition temperaturesabove room temperature or even melting points if a crystallite. It isthe current opinion (and hence their classification) that “soft-segment”prepolymers or resin constituents are associated with the formation ofthe soft-segment phase of the product and conversely that hard-segmentprepolymers or resin constituents are associated with the hard-segmentphase of the product. Structure-property relationships of hard- andsoft-segment phases are described for example by Redman in “Developmentsin Polyurethanes-I” J. M. Buist Ed., Elsevier, London—published 1978.See, e.g., U.S. Pat. No. 5,418,259 (Dow).

Heating may be active heating (e.g., in an oven, such as an electric,gas, or solar oven), or passive heating (e.g., at ambient temperature).Active heating will generally be more rapid than passive heating and insome embodiments is preferred, but passive heating—such as simplymaintaining the intermediate at ambient temperature for a sufficienttime to effect further cure—is in some embodiments preferred.

“Diisocyanate” and “polyisocyanate” are used interchangeably herein andrefer to aliphatic, cycloaliphatic, and aromatic isocyanates that haveat least 2, or in some embodiments more than 2, isocyanate (NCO) groupsper molecule, on average. In some embodiments, the isocyanates have, onaverage, 3 to 6, 8 or 10 or more isocyanate groups per molecule. In someembodiments, the isocyanates may be a hyperbranched or dendrimericisocyanate (e.g., containing more than 10 isocyanate groups permolecule, on average). Common examples of suitable isocyanates include,but are not limited to, methylene diphenyl diisocyanate (MDI), toluenediisocyanate (TDI)), para-phenyl diisocyanate (PPDI),4,4′-dicyclohexylmethane-diisocyanate (HMDI), hexamethylene diisocyanate(HDI), isophorone diisocyanate (IPDI),triphenylmethane-4,4′4″-triisocyanate, tolune-2,4,6-triyl triisocyanate,1,3,5-triazine-2,4,6-triisocyanate, ethyl ester L-lysine triisocyanate,etc., including combinations thereof. Numerous additional examples areknown and are described in, for example, U.S. Pat. Nos. 9,200,108;8,378,053; 7,144,955; 4,075,151, 3,932,342, and in US Patent ApplicationPublication Nos. US 20040067318 and US 20140371406, the disclosures ofall of which are incorporated by reference herein in their entirety.

Oxidizable tin salts useful for carrying out the present inventioninclude, but are not limited to, stannous butanoate, stannous octoate,stannous hexanoate, stannous heptanoate, stannous linoleate, stannousphenyl butanoate, stannous phenyl stearate, stannous phenyl oleate,stannous nonanoate, stannous decanoate, stannous undecanoate, stannousdodecanoate, stannous stearate, stannous oleate, stannous undecenoate,stannous 2-ethylhexoate, dibutyl tin dilaurate, dibutyl tin dioleate,dibutyl tin distearate, dipropyl tin dilaurate, dipropyl tin dioleate,dipropyl tin distearate, dibutyl tin dihexanoate, and combinationsthereof. See also U.S. Pat. Nos. 5,298,532; 4,421,822; and 4,389,514,the disclosures of which are incorporated herein by reference. Inaddition to the foregoing oxidizable tin salts, Lewis acids such asthose described in Chu et al. in Macromolecular Symposia, Volume 95,Issue 1, pages 233-242, June 1995 are known to enhance thepolymerization rates of free-radical polymerizations and are includedherein by reference.

Any suitable filler may be used in connection with the presentinvention, depending on the properties desired in the part or object tobe made. Thus, fillers may be solid or liquid, organic or inorganic, andmay include reactive and non-reactive rubbers: siloxanes,acrylonitrile-butadiene rubbers; reactive and non-reactivethermoplastics (including but not limited to: poly(ether imides),maleimide-styrene terpolymers, polyarylates, polysulfones andpolyethersulfones, etc.) inorganic fillers such as silicates (such astalc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulosenanocrystals, etc., including combinations of all of the foregoing.Suitable fillers include tougheners, such as core-shell rubbers, asdiscussed below.

Tougheners.

One or more polymeric and/or inorganic tougheners can be used as afiller in the present invention. See generally US Patent ApplicationPublication No. 20150215430. The toughener may be uniformly distributedin the form of particles in the cured product. The particles could beless than 5 microns (i±m) in diameter. Such tougheners include, but arenot limited to, those formed from elastomers, branched polymers,hyperbranched polymers, dendrimers, rubbery polymers, rubberycopolymers, block copolymers, core-shell particles, oxides or inorganicmaterials such as clay, polyhedral oligomeric silsesquioxanes (POSS),carbonaceous materials (e.g., carbon black, carbon nanotubes, carbonnanofibers, fullerenes), ceramics and silicon carbides, with or withoutsurface modification or functionalization. Examples of block copolymersinclude the copolymers whose composition is described in U.S. Pat. No.6,894,113 (Court et al., Atofina, 2005) and include “NANOSTRENTH®” SBM(polystyrene-polybutadiene-polymethacrylate), and AMA(polymethacrylate-polybutylacrylate-polymethacrylate), both produced byArkema. Other suitable block copolymers include FORTEGRA® and theamphiphilic block copolymers described in U.S. Pat. No. 7,820,760B2,assigned to Dow Chemical. Examples of known core-shell particles includethe core-shell (dendrimer) particles whose compositions are described inUS20100280151A1 (Nguyen et al., Toray Industries, Inc., 2010) for anamine branched polymer as a shell grafted to a core polymer polymerizedfrom polymerizable monomers containing unsaturated carbon-carbon bonds,core-shell rubber particles whose compositions are described in EP1632533A1 and EP 2123711A1 by Kaneka Corporation, and the “KaneAce MX”product line of such particle/epoxy blends whose particles have apolymeric core polymerized from polymerizable monomers such asbutadiene, styrene, other unsaturated carbon-carbon bond monomer, ortheir combinations, and a polymeric shell compatible with the epoxy,typically polymethylmethacrylate, polyglycidylmethacrylate,polyacrylonitrile or similar polymers, as discussed further below. Alsosuitable as block copolymers in the present invention are the “JSR SX”series of carboxylated polystyrene/polydivinylbenzenes produced by JSRCorporation; “Kureha Paraloid” EXL-2655 (produced by Kureha ChemicalIndustry Co., Ltd.), which is a butadiene alkyl methacrylate styrenecopolymer; “Stafiloid” AC-3355 and TR-2122 (both produced by TakedaChemical Industries, Ltd.), each of which are acrylate methacrylatecopolymers; and “PARALOID” EXL-2611 and EXL-3387 (both produced by Rohm& Haas), each of which are butyl acrylate methyl methacrylatecopolymers. Examples of suitable oxide particles include NANOPOX®produced by nanoresins AG. This is a master blend of functionalizednanosilica particles and an epoxy.

Core-Shell Rubbers.

Core-shell rubbers are particulate materials (particles) having arubbery core. Such materials are known and described in, for example, USPatent Application Publication No. 20150184039, as well as US PatentApplication Publication No. 20150240113, and U.S. Pat. Nos. 6,861,475,7,625,977, 7,642,316, 8,088,245, and elsewhere.

In some embodiments, the core-shell rubber particles are nanoparticles(i.e., having an average particle size of less than 1000 nanometers(nm)). Generally, the average particle size of the core-shell rubbernanoparticles is less than 500 nm, e.g., less than 300 nm, less than 200nm, less than 100 nm, or even less than 50 nm. Typically, such particlesare spherical, so the particle size is the diameter; however, if theparticles are not spherical, the particle size is defined as the longestdimension of the particle.

In some embodiments, the rubbery core can have a glass transitiontemperature (Tg) of less than −25° C., more preferably less than −50°C., and even more preferably less than −70° C. The Tg of the rubberycore may be well below −100° C. The core-shell rubber also has at leastone shell portion that preferably has a Tg of at least 50° C. By “core,”it is meant an internal portion of the core-shell rubber. The core mayform the center of the core-shell particle, or an internal shell ordomain of the core-shell rubber. A shell is a portion of the core-shellrubber that is exterior to the rubbery core. The shell portion (orportions) typically forms the outermost portion of the core-shell rubberparticle. The shell material can be grafted onto the core or iscross-linked. The rubbery core may constitute from 50 to 95%, or from 60to 90%, of the weight of the core-shell rubber particle.

The core of the core-shell rubber may be a polymer or copolymer of aconjugated diene such as butadiene, or a lower alkyl acrylate such asn-butyl-, ethyl-, isobutyl- or 2-ethylhexylacrylate. The core polymermay in addition contain up to 20% by weight of other copolymerizedmono-unsaturated monomers such as styrene, vinyl acetate, vinylchloride, methyl methacrylate, and the like. The core polymer isoptionally cross-linked. The core polymer optionally contains up to 5%of a copolymerized graft-linking monomer having two or more sites ofunsaturation of unequal reactivity, such as diallyl maleate, monoallylfumarate, allyl methacrylate, and the like, at least one of the reactivesites being non-conjugated.

The core polymer may also be a silicone rubber. These materials oftenhave glass transition temperatures below −100° C. Core-shell rubbershaving a silicone rubber core include those commercially available fromWacker Chemie, Munich, Germany, under the trade name GENIOPERL®.

The shell polymer, which is optionally chemically grafted orcross-linked to the rubber core, can be polymerized from at least onelower alkyl methacrylate such as methyl methacrylate, ethyl methacrylateor t-butyl methacrylate. Homopolymers of such methacrylate monomers canbe used. Further, up to 40% by weight of the shell polymer can be formedfrom other monovinylidene monomers such as styrene, vinyl acetate, vinylchloride, methyl acrylate, ethyl acrylate, butyl acrylate, and the like.The molecular weight of the grafted shell polymer can be between 20,000and 500,000.

One suitable type of core-shell rubber has reactive groups in the shellpolymer which can react with an epoxy resin or an epoxy resin hardener.Glycidyl groups are suitable. These can be provided by monomers such asglycidyl methacrylate.

One example of a suitable core-shell rubber is of the type described inUS Patent Application Publication No. 2007/0027233 (EP 1 632 533 A1).Core-shell rubber particles as described therein include a cross-linkedrubber core, in most cases being a cross-linked copolymer of butadiene,and a shell which is preferably a copolymer of styrene, methylmethacrylate, glycidyl methacrylate and optionally acrylonitrile. Thecore-shell rubber is preferably dispersed in a polymer or an epoxyresin, also as described in the document.

Suitable core-shell rubbers include, but are not limited to, those soldby Kaneka Corporation under the designation Kaneka Kane Ace, includingthe Kaneka Kane Ace 15 and 120 series of products, including Kaneka KaneAce MX 120, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, Kaneka KaneAce MX 156, Kaneka Kane Ace MX 170, and Kaneka Kane Ace MX 257 andKaneka Kane Ace MX 120 core-shell rubber dispersions, and mixturesthereof.

I. Polymerizable Liquids: Part A.

Dual cure systems as described herein may include a first curable system(sometimes referred to as “Part A” herein) that is curable by actinicradiation, typically light, and in some embodiments ultraviolet (UV)light). Any suitable polymerizable liquid can be used as the firstcomponent. The liquid (sometimes also referred to as “liquid resin”“ink,” or simply “resin” herein) can include a monomer, particularlyphotopolymerizable and/or free radical polymerizable monomers, and asuitable initiator such as a free radical initiator, and combinationsthereof. Examples include, but are not limited to, acrylics,methacrylics, acrylamides, styrenics, olefins, halogenated olefins,cyclic alkenes, maleic anhydride, alkenes, alkynes, carbon monoxide,functionalized oligomers, multifunctional cute site monomers,functionalized PEGs, etc., including combinations thereof. Examples ofliquid resins, monomers and initiators include but are not limited tothose set forth in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476;7,767,728; 7,649,029; WO 2012129968 Al; CN 102715751 A; JP 2012210408 A.

Acid Catalyzed Polymerizable Liquids.

While in some embodiments as noted above the polymerizable liquidcomprises a free radical polymerizable liquid (in which case aninhibitor may be oxygen as described below), in other embodiments thepolymerizable liquid comprises an acid catalyzed, or cationicallypolymerized, polymerizable liquid. In such embodiments the polymerizableliquid comprises monomers that contain groups suitable for acidcatalysis, such as epoxide groups, vinyl ether groups, etc. Thussuitable monomers include olefins such as methoxyethene,4-methoxystyrene, styrene, 2-methylprop-1-ene, 1,3-butadiene, etc.;heterocycloic monomers (including lactones, lactams, and cyclic amines)such as oxirane, thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane,oxetan-2-one, etc., and combinations thereof. A suitable (generallyionic or non-ionic) photoacid generator (PAG) is included in the acidcatalyzed polymerizable liquid, examples of which include, but are notlimited to onium salts, sulfonium and iodonium salts, etc., such asdiphenyl iodide hexafluorophosphate, diphenyl iodide hexafluoroarsenate,diphenyl iodide hexafluoroantimonate, diphenyl p-methoxyphenyl triflate,diphenyl p-toluenyl triflate, diphenyl p-isobutylphenyl triflate,diphenyl p-tert-butylphenyl triflate, triphenylsulfoniumhexafluororphosphate, triphenylsulfonium hexafluoroarsenate,triphenylsulfonium hexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, etc., including mixtures thereof.See, e.g., U.S. Pat. Nos. 7,824,839; 7,550,246; 7,534,844; 6,692,891;5,374,500; and 5,017,461; see also Photoacid Generator Selection Guidefor the electronics industry and energy curable coatings (BASF 2010).

Hydrogels.

In some embodiments suitable resins includes photocurable hydrogels likepoly(ethylene glycols) (PEG) and gelatins. PEG hydrogels have been usedto deliver a variety of biologicals, including growth factors; however,a great challenge facing PEG hydrogels crosslinked by chain growthpolymerizations is the potential for irreversible protein damage.Conditions to maximize release of the biologicals from photopolymerizedPEG diacrylate hydrogels can be enhanced by inclusion of affinitybinding peptide sequences in the monomer resin solutions, prior tophotopolymerization allowing sustained delivery. Gelatin is a biopolymerfrequently used in food, cosmetic, pharmaceutical and photographicindustries. It is obtained by thermal denaturation or chemical andphysical degradation of collagen. There are three kinds of gelatin,including those found in animals, fish and humans. Gelatin from the skinof cold water fish is considered safe to use in pharmaceuticalapplications. UV or visible light can be used to crosslink appropriatelymodified gelatin. Methods for crosslinking gelatin include curederivatives from dyes such as Rose Bengal.

Photocurable Silicone Resins.

A suitable resin includes photocurable silicones. UV cure siliconerubber, such as Siliopren™ UV Cure Silicone Rubber can be used as canLOCTITE™ Cure Silicone adhesives sealants. Applications include opticalinstruments, medical and surgical equipment, exterior lighting andenclosures, electrical connectors/sensors, fiber optics, gaskets, andmolds.

Biodegradable Resins.

Biodegradable resins are particularly important for implantable devicesto deliver drugs or for temporary performance applications, likebiodegradable screws and stents (U.S. Pat. Nos. 7,919,162; 6,932,930).Biodegradable copolymers of lactic acid and glycolic acid (PLGA) can bedissolved in PEG di(meth)acrylate to yield a transparent resin suitablefor use. Polycaprolactone and PLGA oligomers can be functionalized withacrylic or methacrylic groups to allow them to be effective resins foruse.

Photocurable Polyurethanes.

A particularly useful resin is photocurable polyurethanes (includingpolyureas, and copolymers of polyurethanes and polyureas (e.g.,poly(urethane-urea)). A photopolymerizable polyurethane/polyureacomposition comprising (1) a polyurethane based on an aliphaticdiisocyanate, poly(hexamethylene isophthalate glycol) and, optionally,1,4-butanediol; (2) a polyfunctional acrylic ester; (3) aphotoinitiator; and (4) an anti-oxidant, can be formulated so that itprovides a hard, abrasion-resistant, and stain-resistant material (U.S.Pat. No. 4,337,130). Photocurable thermoplastic polyurethane elastomersincorporate photoreactive diacetylene diols as chain extenders.

High Performance Resins.

In some embodiments, high performance resins are used. Such highperformance resins may sometimes require the use of heating to meltand/or reduce the viscosity thereof, as noted above and discussedfurther below. Examples of such resins include, but are not limited to,resins for those materials sometimes referred to as liquid crystallinepolymers of esters, ester-imide, and ester-amide oligomers, as describedin U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resins are sometimesemployed as high-temperature thermoset resins, in the present inventionthey further comprise a suitable photoinitiator such as benzophenone,anthraquinone, and fluorenone initiators (including derivativesthereof), to initiate cross-linking on irradiation, as discussed furtherbelow.

Additional Example Resins.

Particularly useful resins for dental applications include EnvisionTEC'sClear Guide, EnvisionTEC's E-Denstone Material. Particularly usefulresins for hearing aid industries include EnvisionTEC's e-Shell 300Series of resins. Particularly useful resins include EnvisionTEC'sHTM140IV High Temperature Mold Material for use directly with vulcanizedrubber in molding/casting applications. A particularly useful materialfor making tough and stiff parts includes EnvisionTEC's RC31 resin.Particularly useful resin for investment casting applications includeEnvisionTEC's Easy Cast EC500 resin and MadeSolid FireCast resin.

Additional Resin Ingredients.

The liquid resin or polymerizable material can have solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. The particles can bemetallic, organic/polymeric, inorganic, or composites or mixturesthereof. The particles can be nonconductive, semi-conductive, orconductive (including metallic and non-metallic or polymer conductors);and the particles can be magnetic, ferromagnetic, paramagnetic, ornonmagnetic. The particles can be of any suitable shape, includingspherical, elliptical, cylindrical, etc. The particles can be of anysuitable size (for example, ranging from 1 nm to 20 μm averagediameter).

The particles can comprise an active agent or detectable compound asdescribed below, though these may also be provided dissolved solubilizedin the liquid resin as also discussed below. For example, magnetic orparamagnetic particles or nanoparticles can be employed.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Non-Reactive Light Absorbers.

In some embodiments, polymerizable liquids for carrying out the presentinvention include a non-reactive pigment or dye that absorbs light,particularly UV light. Suitable examples of such light absorbersinclude, but are not limited to: (i) titanium dioxide (e.g., included inan amount of from 0.05 or 0.1 to 1 or 5 percent by weight), (ii) carbonblack (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percentby weight), and/or (iii) an organic ultraviolet light absorber such as ahydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide,benzophenone, thioxanthone, hydroxypenyltriazine, and/or benzotriazoleultraviolet light absorber (e.g., Mayzo BLS1326) (e.g., included in anamount of 0.001 or 0.005 to 1, 2 or 4 percent by weight). Examples ofsuitable organic ultraviolet light absorbers include, but are notlimited to, those described in U.S. Pat. Nos. 3,213,058; 6,916,867;7,157,586; and 7,695,643, the disclosures of which are incorporatedherein by reference.

Inhibitors of Polymerization.

Inhibitors or polymerization inhibitors for use in the present inventionmay be in the form of a liquid or a gas. In some embodiments, gasinhibitors are preferred. In some embodiments, liquid inhibitors such asoils or lubricants (e.g., fluorinated oils such as perfluoropolyethers)may be employed, as inhibitors (or as release layers that maintain aliquid interface). The specific inhibitor will depend upon the monomerbeing polymerized and the polymerization reaction. For free radicalpolymerization monomers, the inhibitor can conveniently be oxygen, whichcan be provided in the form of a gas such as air, a gas enriched inoxygen (optionally but in some embodiments preferably containingadditional inert gases to reduce combustibility thereof), or in someembodiments pure oxygen gas. In alternate embodiments, such as where themonomer is polymerized by a photoacid generator initiator, the inhibitorcan be a base such as ammonia, trace amines (e.g., methyl amine, ethylamine, di and trialkyl amines such as dimethyl amine, diethyl amine,trimethyl amine, triethyl amine, etc.), or carbon dioxide, includingmixtures or combinations thereof.

Polymerizable Liquids Carrying Live Cells.

In some embodiments, the polymerizable liquid may carry live cells as“particles” therein. Such polymerizable liquids are generally aqueous,and may be oxygenated, and may be considered as “emulsions” where thelive cells are the discrete phase. Suitable live cells may be plantcells (e.g., monocot, dicot), animal cells (e.g., mammalian, avian,amphibian, reptile cells), microbial cells (e.g., prokaryote, eukaryote,protozoal, etc.), etc. The cells may be of differentiated cells from orcorresponding to any type of tissue (e.g., blood, cartilage, bone,muscle, endocrine gland, exocrine gland, epithelial, endothelial, etc.),or may be undifferentiated cells such as stem cells or progenitor cells.In such embodiments the polymerizable liquid can be one that forms ahydrogel, including but not limited to those described in U.S. Pat. Nos.7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313; etc.

II. Apparatus.

A non-limiting embodiment of an apparatus of the invention is shown inFIG. 2. It comprises a radiation source 11 such as a digital lightprocessor (DLP) providing electromagnetic radiation 12 which thoughreflective mirror 13 illuminates a build chamber defined by wall 14 anda rigid or flexible build plate 15 forming the bottom of the buildchamber, which build chamber is filled with liquid resin 16. The bottomof the chamber 15 is constructed of a build plate comprising a rigid orflexible semipermeable member as discussed further below. The top of theobject under construction 17 is attached to a carrier 18. The carrier isdriven in the vertical direction by linear stage 19, although alternatestructures can be used as discussed below.

A liquid resin reservoir, tubing, pumps, liquid level sensors and/orvalves can be included to replenish the pool of liquid resin in thebuild chamber (not shown for clarity) though in some embodiments asimple gravity feed may be employed. Drives/actuators for the carrier orlinear stage, along with associated wiring, can be included inaccordance with known techniques (again not shown for clarity). Thedrives/actuators, radiation source, and in some embodiments pumps andliquid level sensors can all be operatively associated with a suitablecontroller, again in accordance with known techniques.

Build plates 15 used to carry out the present invention generallycomprise or consist of a (typically rigid or solid, stationary, and/orfixed, although in some embodiments flexible) semipermeable (or gaspermeable) member, alone or in combination with one or more additionalsupporting substrates (e.g., clamps and tensioning members to tensionand stabilize an otherwise flexible semipermeable material). Thesemipermeable member can be made of any suitable material that isoptically transparent at the relevant wavelengths (or otherwisetransparent to the radiation source, whether or not it is visuallytransparent as perceived by the human eye—i.e., an optically transparentwindow may in some embodiments be visually opaque), including but notlimited to porous or microporous glass, and the rigid gas permeablepolymers used for the manufacture of rigid gas permeable contact lenses.See, e.g., Norman G. Gaylord, U.S. Pat. No. RE31,406; see also U.S. Pat.Nos. 7,862,176; 7,344,731; 7,097,302; 5,349,394; 5,310,571; 5,162,469;5,141,665; 5,070,170; 4,923,906; and 4,845,089. In some embodiments suchmaterials are characterized as glassy and/or amorphous polymers and/orsubstantially crosslinked that they are essentially non-swellable.Preferably the semipermeable member is formed of a material that doesnot swell when contacted to the liquid resin or material to bepolymerized (i.e., is “non-swellable”). Suitable materials for thesemipermeable member include amorphous fluoropolymers, such as thosedescribed in U.S. Pat. Nos. 5,308,685 and 5,051,115. For example, suchfluoropolymers are particularly useful over silicones that wouldpotentially swell when used in conjunction with organic liquid resininks to be polymerized. For some liquid resin inks, such as moreaqueous-based monomeric systems and/or some polymeric resin ink systemsthat have low swelling tendencies, silicone based window materials maybesuitable. The solubility or permeability of organic liquid resin inkscan be dramatically decreased by a number of known parameters includingincreasing the crosslink density of the window material or increasingthe molecular weight of the liquid resin ink. In some embodiments thebuild plate may be formed from a thin film or sheet of material which isflexible when separated from the apparatus of the invention, but whichis clamped and tensioned when installed in the apparatus (e.g., with atensioning ring) so that it is tensioned and stabilized in theapparatus. Particular materials include TEFLON AF® fluoropolymers,commercially available from DuPont. Additional materials includeperfluoropolyether polymers such as described in U.S. Pat. Nos.8,268,446; 8,263,129; 8,158,728; and 7,435,495.

It will be appreciated that essentially all solid materials, and most ofthose described above, have some inherent “flex” even though they may beconsidered “rigid,” depending on factors such as the shape and thicknessthereof and environmental factors such as the pressure and temperatureto which they are subjected. In addition, the terms “stationary” or“fixed” with respect to the build plate is intended to mean that nomechanical interruption of the process occurs, or no mechanism orstructure for mechanical interruption of the process (as in alayer-by-layer method or apparatus) is provided, even if a mechanism forincremental adjustment of the build plate (for example, adjustment thatdoes not lead to or cause collapse of the gradient of polymerizationzone) is provided.

The semipermeable member typically comprises a top surface portion, abottom surface portion, and an edge surface portion. The build surfaceis on the top surface portion; and the feed surface may be on one, two,or all three of the top surface portion, the bottom surface portion,and/or the edge surface portion. In the embodiment illustrated in FIG. 2the feed surface is on the bottom surface portion, but alternateconfigurations where the feed surface is provided on an edge, and/or onthe top surface portion (close to but separate or spaced away from thebuild surface) can be implemented with routine skill.

The semipermeable member has, in some embodiments, a thickness of from0.01, 0.1 or 1 millimeters to 10 or 100 millimeters, or more, dependingupon the size of the item being fabricated, whether or not it islaminated to or in contact with an additional supporting plate such asglass, etc., as discussed further below.

The permeability of the semipermeable member to the polymerizationinhibitor will depend upon conditions such as the pressure of theatmosphere and/or inhibitor, the choice of inhibitor, the rate or speedof fabrication, etc. In general, when the inhibitor is oxygen, thepermeability of the semipermeable member to oxygen may be from 10 or 20Barrers, up to 1000 or 2000 Barrers, or more. For example, asemipermeable member with a permeability of 10 Barrers used with a pureoxygen, or highly enriched oxygen, atmosphere under a pressure of 150PSI may perform substantially the same as a semipermeable member with apermeability of 500 Barrers when the oxygen is supplied from the ambientatmosphere under atmospheric conditions.

Thus, the semipermeable member may comprise a flexible polymer film(having any suitable thickness, e.g., from 0.001, 0.01, 0.05, 0.1 or 1millimeters to 1, 5, 10, or 100 millimeters, or more), and the buildplate may further comprise a tensioning member (e.g., a peripheral clampand an operatively associated strain member or stretching member, as ina “drum head”; a plurality of peripheral clamps, etc., includingcombinations thereof) connected to the polymer film and to fix andtension, stabilize or rigidify the film (e.g., at least sufficiently sothat the film does not stick to the object as the object is advanced andresiliently or elastically rebound therefrom). The film has a topsurface and a bottom surface, with the build surface on the top surfaceand the feed surface preferably on the bottom surface. In otherembodiments, the semipermeable member comprises: (i) a polymer filmlayer (having any suitable thickness, e.g., from 0.001, 0.01, 0.1 or 1millimeters to 5, 10 or 100 millimeters, or more), having a top surfacepositioned for contacting the polymerizable liquid and a bottom surface,and (ii) a gas permeable, optically transparent supporting member(having any suitable thickness, e.g., from 0.01, 0.1 or 1 millimeters to10, 100, or 200 millimeters, or more), contacting the film layer bottomsurface. The supporting member has a top surface contacting the filmlayer bottom surface, and the supporting member has a bottom surfacewhich may serve as the feed surface for the polymerization inhibitor.Any suitable materials that are semipermeable (that is, permeable to thepolymerization inhibitor) may be used. For example, the polymer film orpolymer film layer may be a fluoropolymer film, such as an amorphousthermoplastic fluoropolymer like TEFLON AF 1600™ or TEFLON AF 2400™fluoropolymer films, or perfluoropolyether (PFPE), particularly acrosslinked PFPE film, or a crosslinked silicone polymer film. Thesupporting member comprises a silicone or crosslinked silicone polymermember such as a polydimethylsiloxane polydimethylsiloxane member, a gaspermeable polymer member, or a porous or microporous glass member. Filmscan be laminated or clamped directly to the rigid supporting memberwithout adhesive (e.g., using PFPE and PDMS materials), or silanecoupling agents that react with the upper surface of a PDMS layer can beutilized to adhere to the first polymer film layer. UV-curable,acrylate-functional silicones can also be used as a tie layer betweenUV-curable PFPEs and rigid PDMS supporting layers.

When configured for placement in the apparatus, the carrier defines a“build region” on the build surface, within the total area of the buildsurface. Because lateral “throw” (e.g., in the X and/or Y directions) isnot required in the present invention to break adhesion betweensuccessive layers, as in the Joyce and Chen devices noted previously,the area of the build region within the build surface may be maximized(or conversely, the area of the build surface not devoted to the buildregion may be minimized). Hence in some embodiments, the total surfacearea of the build region can occupy at least fifty, sixty, seventy,eighty, or ninety percent of the total surface area of the buildsurface.

As shown in FIG. 2, the various components are mounted on a support orframe assembly 20. While the particular design of the support or frameassembly is not critical and can assume numerous configurations, in theillustrated embodiment it is comprised of a base 21 to which theradiation source 11 is securely or rigidly attached, a vertical member22 to which the linear stage is operatively associated, and a horizontaltable 23 to which wall 14 is removably or securely attached (or on whichthe wall is placed), and with the build plate fixed, either permanentlyor removably, to form the build chamber as described above.

As noted above, the build plate can consist of a single unitary andintegral piece of a semipermeable member, or can comprise additionalmaterials. For example, a porous or microporous glass can be laminatedor fixed to a semipermeable material. Or, a semipermeable member as anupper portion can be fixed to a transparent lower member having purgingchannels formed therein for feeding gas carrying the polymerizationinhibitor to the semipermeable member (through which it passes to thebuild surface to facilitate the formation of a release layer ofunpolymerized liquid material, as noted above and below). Such purgechannels may extend fully or partially through the base plate: Forexample, the purge channels may extend partially into the base plate,but then end in the region directly underlying the build surface toavoid introduction of distortion. Specific geometries will depend uponwhether the feed surface for the inhibitor into the semipermeable memberis located on the same side or opposite side as the build surface, on anedge portion thereof, or a combination of several thereof.

Any suitable radiation source (or combination of sources) can be used,depending upon the particular resin employed, including electron beamand ionizing radiation sources. In a preferred embodiment the radiationsource is an actinic radiation source, such as one or more lightsources, and in particular one or more ultraviolet light sources. Anysuitable light source can be used, such as incandescent lights,fluorescent lights, phosphorescent or luminescent lights, a laser,light-emitting diode, etc., including arrays thereof. The light sourcepreferably includes a pattern-forming element operatively associatedwith a controller, as noted above. In some embodiments, the light sourceor pattern forming element comprises a digital (or deformable)micromirror device (DMD) with digital light processing (DLP), a spatialmodulator (SLM), or a microelectromechanical system (MEMS) mirror array,a liquid crystal display (LCD) panel, a mask (aka a reticle), asilhouette, or a combination thereof. See, U.S. Pat. No. 7,902,526.Preferably the light source comprises a spatial light modulation arraysuch as a liquid crystal light valve array or micromirror array or DMD(e.g., with an operatively associated digital light processor, typicallyin turn under the control of a suitable controller), configured to carryout exposure or irradiation of the polymerizable liquid without a mask,e.g., by maskless photolithography. See, e.g., U.S. Pat. Nos. 6,312,134;6,248,509; 6,238,852; and 5,691,541.

In some embodiments, as discussed further below, there may be movementin the X and/or Y directions concurrently with movement in the Zdirection, with the movement in the X and/or Y direction hence occurringduring polymerization of the polymerizable liquid (this is in contrastto the movement described in Y. Chen et al., or M. Joyce, supra, whichis movement between prior and subsequent polymerization steps for thepurpose of replenishing polymerizable liquid). In the present inventionsuch movement may be carried out for purposes such as reducing “burn in”or fouling in a particular zone of the build surface.

Because an advantage of some embodiments of the present invention isthat the size of the build surface on the semipermeable member (i.e.,the build plate or window) may be reduced due to the absence of arequirement for extensive lateral “throw” as in the Joyce or Chendevices noted above, in the methods, systems and apparatus of thepresent invention lateral movement (including movement in the X and/or Ydirection or combination thereof) of the carrier and object (if suchlateral movement is present) is preferably not more than, or less than,80, 70, 60, 50, 40, 30, 20, or even 10 percent of the width (in thedirection of that lateral movement) of the build region.

While in some embodiments the carrier is mounted on an elevator toadvance up and away from a stationary build plate, on other embodimentsthe converse arrangement may be used: That is, the carrier may be fixedand the build plate lowered to thereby advance the carrier awaytherefrom. Numerous different mechanical configurations will be apparentto those skilled in the art to achieve the same result.

Depending on the choice of material from which the carrier isfabricated, and the choice of polymer or resin from which the article ismade, adhesion of the article to the carrier may sometimes beinsufficient to retain the article on the carrier through to completionof the finished article or “build.” For example, an aluminum carrier mayhave lower adhesion than a poly(vinyl chloride) (or “PVC”) carrier.Hence one solution is to employ a carrier comprising a PVC on thesurface to which the article being fabricated is polymerized. If thispromotes too great an adhesion to conveniently separate the finishedpart from the carrier, then any of a variety of techniques can be usedto further secure the article to a less adhesive carrier, including butnot limited to the application of adhesive tape such as “Greener MaskingTape for Basic Painting #2025 High adhesion” to further secure thearticle to the carrier during fabrication.

III. Controller and Process Control.

The methods and apparatus of the invention can include process steps andapparatus features to implement process control, including feedback andfeed-forward control, to, for example, enhance the speed and/orreliability of the method.

A controller for use in carrying out the present invention may beimplemented as hardware circuitry, software, or a combination thereof.In one embodiment, the controller is a general purpose computer thatruns software, operatively associated with monitors, drives, pumps, andother components through suitable interface hardware and/or software.Suitable software for the control of a three-dimensional printing orfabrication method and apparatus as described herein includes, but isnot limited to, the ReplicatorG open source 3d printing program,3DPrint™ controller software from 3D systems, Slic3r, Skeinforge,KISSlicer, Repetier-Host, PrintRun, Cura, etc., including combinationsthereof.

Process parameters to directly or indirectly monitor, continuously orintermittently, during the process (e.g., during one, some or all of thefilling, irradiating and advancing steps) include, but are not limitedto, irradiation intensity, temperature of carrier, polymerizable liquidin the build zone, temperature of growing product, temperature of buildplate, pressure, speed of advance, pressure, force (e.g., exerted on thebuild plate through the carrier and product being fabricated), strain(e.g., exerted on the carrier by the growing product being fabricated),thickness of release layer, etc.

Known parameters that may be used in feedback and/or feed-forwardcontrol systems include, but are not limited to, expected consumption ofpolymerizable liquid (e.g., from the known geometry or volume of thearticle being fabricated), degradation temperature of the polymer beingformed from the polymerizable liquid, etc.

Process conditions to directly or indirectly control, continuously orstep-wise, in response to a monitored parameter, and/or known parameters(e.g., during any or all of the process steps noted above), include, butare not limited to, rate of supply of polymerizable liquid, temperature,pressure, rate or speed of advance of carrier, intensity of irradiation,duration of irradiation (e.g., for each “slice”), etc.

For example, the temperature of the polymerizable liquid in the buildzone, or the temperature of the build plate, can be monitored, directlyor indirectly with an appropriate thermocouple, non-contact temperaturesensor (e.g., an infrared temperature sensor), or other suitabletemperature sensor, to determine whether the temperature exceeds thedegradation temperature of the polymerized product. If so, a processparameter may be adjusted through a controller to reduce the temperaturein the build zone and/or of the build plate. Suitable process parametersfor such adjustment may include: decreasing temperature with a cooler,decreasing the rate of advance of the carrier, decreasing intensity ofthe irradiation, decreasing duration of radiation exposure, etc.

In addition, the intensity of the irradiation source (e.g., anultraviolet light source such as a mercury lamp) may be monitored with aphotodetector to detect a decrease of intensity from the irradiationsource (e.g., through routine degradation thereof during use). Ifdetected, a process parameter may be adjusted through a controller toaccommodate the loss of intensity. Suitable process parameters for suchadjustment may include: increasing temperature with a heater, decreasingthe rate of advance of the carrier, increasing power to the lightsource, etc.

As another example, control of temperature and/or pressure to enhancefabrication time may be achieved with heaters and coolers (individually,or in combination with one another and separately responsive to acontroller), and/or with a pressure supply (e.g., pump, pressure vessel,valves and combinations thereof) and/or a pressure release mechanismsuch as a controllable valve (individually, or in combination with oneanother and separately responsive to a controller).

In some embodiments, the controller is configured to maintain thegradient of polymerization zone described herein (see, e.g., FIG. 1)throughout the fabrication of some or all of the final product. Thespecific configuration (e.g., times, rate or speed of advancing,radiation intensity, temperature, etc.) will depend upon factors such asthe nature of the specific polymerizable liquid and the product beingcreated. Configuration to maintain the gradient of polymerization zonemay be carried out empirically, by entering a set of process parametersor instructions previously determined, or determined through a series oftest runs or “trial and error”; configuration may be provided throughpre-determined instructions; configuration may be achieved by suitablemonitoring and feedback (as discussed above), combinations thereof, orin any other suitable manner.

In some embodiments, a method and apparatus as described above may becontrolled by a software program running in a general purpose computerwith suitable interface hardware between that computer and the apparatusdescribed above. Numerous alternatives are commercially available.Non-limiting examples of one combination of components is shown in FIG.3-FIG. 5, where “Microcontroller” is Parallax Propeller, the StepperMotor Driver is Sparkfun EasyDriver, the LED Driver is a Luxeon SingleLED Driver, the USB to Serial is a Parallax USB to Serial converter, andthe DLP System is a Texas Instruments LightCrafter system.

IV. General Methods.

The three-dimensional intermediate is preferably formed from resins asdescribed above by additive manufacturing, typically bottom-up ortop-down additive manufacturing. In general, top-down three-dimensionalfabrication is carried out by:

(a) providing a polymerizable liquid reservoir having a polymerizableliquid fill level and a carrier positioned in the reservoir, the carrierand the fill level defining a build region therebetween;

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light to form a solid polymerscaffold from the first component and also advancing (typicallylowering) the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object and containing said secondsolidifiable component (e.g., a second reactive component) carried inthe scaffold in unsolidified and/or uncured form.

A wiper blade, doctor blade, or optically transparent (rigid orflexible) window, may optionally be provided at the fill level tofacilitate leveling of the polymerizable liquid, in accordance withknown techniques. In the case of an optically transparent window, thewindow provides a build surface against which the three-dimensionalintermediate is formed, analogous to the build surface in bottom-upthree-dimensional fabrication as discussed below.

In general, bottom-up three-dimensional fabrication is carried out by:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light through said opticallytransparent member to form a solid polymer scaffold from the firstcomponent and also advancing (typically raising) the carrier away fromthe build surface to form a three-dimensional intermediate having thesame shape as, or a shape to be imparted to, the three-dimensionalobject and containing said second solidifiable component (e.g., a secondreactive component) carried in the scaffold in unsolidified and/oruncured form.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as implemented in the context of the present invention, thebuild surface is stationary during the formation of thethree-dimensional intermediate; in other embodiments of bottom-upthree-dimensional fabrication as implemented in the context of thepresent invention, the build surface is tilted, slid, flexed and/orpeeled, and/or otherwise translocated or released from the growingthree-dimensional intermediate, usually repeatedly, during formation ofthe three-dimensional intermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as carried out in the context of the present invention, thepolymerizable liquid (or resin) is maintained in liquid contact withboth the growing three dimensional intermediate and the build surfaceduring both the filling and irradiating steps, during fabrication ofsome of, a major portion of, or all of the three-dimensionalintermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as carried out in the context of the present invention, thegrowing three-dimensional intermediate is fabricated in a layerlessmanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light) during at least a portion of the formationof the three-dimensional intermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as carried out in the context of the present invention, thegrowing three-dimensional intermediate is fabricated in a layer-by-layermanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light), during at least a portion of the formationof the three-dimensional intermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication employing a rigid or flexible optically transparent window,a lubricant or immiscible liquid may be provided between the window andthe polymerizable liquid (e.g., a fluorinated fluid or oil such as aperfluoropolyether oil).

From the foregoing it will be appreciated that, in some embodiments ofbottom-up or top-down three-dimensional fabrication as carried out inthe context of the present invention, the growing three-dimensionalintermediate is fabricated in a layerless manner during the formation ofat least one portion thereof, and that same growing three-dimensionalintermediate is fabricated in a layer-by-layer manner during theformation of at least one other portion thereof.

Thus, operating mode may be changed once, or on multiple occasions,between layerless fabrication and layer-by-layer fabrication, as desiredby operating conditions such as part geometry.

In some embodiments, the intermediate is formed by continuous liquidinterface production (CLIP), as discussed further below.

As noted above, the present invention provides (in some embodiments) amethod of forming a three-dimensional object, comprising the steps of:(a) providing a carrier and a build plate, the build plate comprising asemipermeable member, the semipermeable member comprising a buildsurface and a feed surface separate from the build surface, with thebuild surface and the carrier defining a build region therebetween, andwith the feed surface in fluid contact with a polymerization inhibitor,then (concurrently and/or sequentially) (b) filling the build regionwith a polymerizable liquid, the polymerizable liquid contacting thebuild segment, (c) irradiating the build region through the build plateto produce a solid polymerized region in the build region, with a liquidfilm release layer comprised of the polymerizable liquid formed betweenthe solid polymerized region and the build surface, the polymerizationof which liquid film is inhibited by the polymerization inhibitor, and(d) advancing the carrier with the polymerized region adhered theretoaway from the build surface on the stationary build plate to create asubsequent build region between the polymerized region and the top zone.In general the method includes (e) continuing and/or repeating steps (b)through (d) to produce a subsequent polymerized region adhered to aprevious polymerized region until the continued or repeated depositionof polymerized regions adhered to one another forms thethree-dimensional object.

Since no mechanical release of a release layer is required, or nomechanical movement of a build surface to replenish oxygen or otherinhibitor is required, the method can be carried out in a continuousfashion, though it will be appreciated that the individual steps notedabove may be carried out sequentially, concurrently, or a combinationthereof. Indeed, the rate of steps can be varied over time dependingupon factors such as the density and/or complexity of the region underfabrication.

Also, since mechanical release from a window or from a release layergenerally requires that the carrier be advanced a greater distance fromthe build plate than desired for the next irradiation step, whichenables the window to be recoated, and then return of the carrier backcloser to the build plate (e.g., a “two steps forward one step back”operation), the present invention in some embodiments permitselimination of this “back-up” step and allows the carrier to be advancedunidirectionally, or in a single direction, without intervening movementof the window for re-coating, or “snapping” of a pre-formed elasticrelease-layer. However, in other embodiments of the invention,reciprocation is utilized not for the purpose of obtaining release, butfor the purpose of more rapidly filling or pumping polymerizable liquidinto the build region.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or thegradient of polymerization zone and the dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore.

Thus the gradient of polymerization zone may be thick or thin dependingon the particular process conditions at that time. Where the gradient ofpolymerization zone is thin, it may also be described as an activesurface on the bottom of the growing three-dimensional object, withwhich monomers can react and continue to form growing polymer chainstherewith. In some embodiments, the gradient of polymerization zone, oractive surface, is maintained (while polymerizing steps continue) for atime of at least 5, 10, 15, 20 or 30 seconds, up to 5, 10, 15 or 20minutes or more, or until completion of the three-dimensional product.

The method may further comprise the step of disrupting the gradient ofpolymerization zone for a time sufficient to form a cleavage line in thethree-dimensional object (e.g., at a predetermined desired location forintentional cleavage, or at a location in the object where prevention ofcleavage or reduction of cleavage is non-critical), and then reinstatingthe gradient of polymerization zone (e.g., by pausing, and resuming, theadvancing step, increasing, then decreasing, the intensity ofirradiation, and combinations thereof).

In some embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.)

In other embodiments of the invention, the advancing step is carried outcontinuously, at a uniform or variable rate.

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.11, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending on factors such as temperature, pressure, structure of thearticle being produced, intensity of radiation, etc

As described further below, in some embodiments the filling step iscarried out by forcing the polymerizable liquid into the build regionunder pressure. In such a case, the advancing step or steps may becarried out at a rate or cumulative or average rate of at least 0.1, 1,10, 50, 100, 500 or 1000 microns per second, or more. In general, thepressure may be whatever is sufficient to increase the rate of theadvancing step(s) at least 2, 4, 6, 8 or 10 times as compared to themaximum rate of repetition of the advancing steps in the absence of thepressure. Where the pressure is provided by enclosing an apparatus suchas described above in a pressure vessel and carrying the process out ina pressurized atmosphere (e.g., of air, air enriched with oxygen, ablend of gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40pounds per square inch (PSI) up to, 200, 300, 400 or 500 PSI or more,may be used. For fabrication of large irregular objects higher pressuresmay be less preferred as compared to slower fabrication times due to thecost of a large high pressure vessel. In such an embodiment, both thefeed surface and the polymerizable liquid can be in fluid contact withthe same compressed gas (e.g., one comprising from 20 to 95 percent byvolume of oxygen, the oxygen serving as the polymerization inhibitor.

On the other hand, when smaller items are fabricated, or a rod or fiberis fabricated that can be removed or exited from the pressure vessel asit is produced through a port or orifice therein, then the size of thepressure vessel can be kept smaller relative to the size of the productbeing fabricated and higher pressures can (if desired) be more readilyutilized.

As noted above, the irradiating step is in some embodiments carried outwith patterned irradiation. The patterned irradiation may be a fixedpattern or may be a variable pattern created by a pattern generator(e.g., a DLP) as discussed above, depending upon the particular itembeing fabricated.

When the patterned irradiation is a variable pattern rather than apattern that is held constant over time, then each irradiating step maybe any suitable time or duration depending on factors such as theintensity of the irradiation, the presence or absence of dyes in thepolymerizable material, the rate of growth, etc. Thus in someembodiments each irradiating step can be from 0.001, 0.01, 0.1, 1 or 10microseconds, up to 1, 10, or 100 minutes, or more, in duration. Theinterval between each irradiating step is in some embodiments preferablyas brief as possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds upto 0.1, 1, or 10 seconds. In example embodiments, the pattern may varyhundreds, thousands or millions of times to impart shape changes on thethree-dimensional object being formed. In addition, in exampleembodiments, the pattern generator may have high resolution withmillions of pixel elements that can be varied to change the shape thatis imparted. For example, the pattern generator may be a DLP with morethan 1,000 or 2,000 or 3,000 or more rows and/or more than 1,000 or2,000 or 3,000 or more columns of micromirrors, or pixels in a liquidcrystal display panel, that can be used to vary the shape. In exampleembodiments, the three-dimensional object may be formed through thegradient of polymerization allowing the shape changes to be impartedwhile continuously printing. In example embodiments, this allows complexthree-dimensional objects to be formed at high speed with asubstantially continuous surface without cleavage lines or seams. Insome examples, thousands or millions of shape variations may be impartedon the three-dimensional object being formed without cleavage lines orseams across a length of the object being formed of more than 1 mm, 1cm, 10 cm or more or across the entire length of the formed object. Inexample embodiments, the object may be continuously formed through thegradient of polymerization at a rate of more than 1, 10, 100, 1000,10000 or more microns per second.

In some embodiments the build surface is flat; in others the buildsurface is irregular such as convexly or concavely curved, or has wallsor trenches formed therein. In either case the build surface may besmooth or textured.

Curved and/or irregular build plates or build surfaces can be used infiber or rod formation, to provide different materials to a singleobject being fabricated, that is, different polymerizable liquids to thesame build surface through channels or trenches formed in the buildsurface, each associated with a separate liquid supply, etc.

Carrier Feed Channels for Polymerizable Liquid

While polymerizable liquid may be provided directly to the build platefrom a liquid conduit and reservoir system, in some embodiments thecarrier includes one or more feed channels therein. The carrier feedchannels are in fluid communication with the polymerizable liquidsupply, for example a reservoir and associated pump. Different carrierfeed channels may be in fluid communication with the same supply andoperate simultaneously with one another, or different carrier feedchannels may be separately controllable from one another (for example,through the provision of a pump and/or valve for each). Separatelycontrollable feed channels may be in fluid communication with areservoir containing the same polymerizable liquid, or may be in fluidcommunication with a reservoir containing different polymerizableliquids. Through the use of valve assemblies, different polymerizableliquids may in some embodiments be alternately fed through the same feedchannel, if desired.

V. Reciprocal Feed of Polymerizable Liquid.

In an embodiment of the present invention, the carrier is verticallyreciprocated with respect to the build surface to enhance or speed therefilling of the build region with the polymerizable liquid.

In some embodiments, the vertically reciprocating step, which comprisesan upstroke and a downstroke, is carried out with the distance of travelof the upstroke being greater than the distance of travel of thedownstroke, to thereby concurrently carry out the advancing step (thatis, driving the carrier away from the build plate in the Z dimension) inpart or in whole.

In some embodiments, the speed of the upstroke gradually accelerates(that is, there is provided a gradual start and/or gradual accelerationof the upstroke) over a period of at least 20, 30, 40, or 50 percent ofthe total time of the upstroke, until the conclusion of the upstroke, orthe change of direction which represents the beginning of thedownstroke. Stated differently, the upstroke begins, or starts, gentlyor gradually.

In some embodiments, the speed of the downstroke gradually decelerates(that is, there is provided a gradual termination and/or gradualdeceleration of the downstroke) over a period of at least 20, 30, 40, or50 percent of the total time of the downstroke. Stated differently, thedownstroke concludes, or ends, gently or gradually.

While in some embodiments there is an abrupt end, or abruptdeceleration, of the upstroke, and an abrupt beginning or decelerationof the downstroke (e.g., a rapid change in vector or direction of travelfrom upstroke to downstroke), it will be appreciated that gradualtransitions may be introduced here as well (e.g., through introductionof a “plateau” or pause in travel between the upstroke and downstroke).It will also be appreciated that, while the reciprocating step may be asingle upstroke and downstroke, the reciprocations may occur in linkedgroups thereof, of the same or different amplitude and frequency.

In some embodiments, the vertically reciprocating step is carried outover a total time of from 0.01 or 0.1 seconds up to 1 or 10 seconds(e.g., per cycle of an upstroke and a downstroke).

In some embodiments, the upstroke distance of travel is from 0.02 or 0.2millimeters (or or 200 microns) to 1 or 10 millimeters (or 1000 to10,000 microns). The distance of travel of the downstroke may be thesame as, or less than, the distance of travel of the upstroke, where alesser distance of travel for the downstroke serves to achieve theadvancing of the carrier away from the build surface as thethree-dimensional object is gradually formed.

Preferably the vertically reciprocating step, and particularly theupstroke thereof, does not cause the formation of gas bubbles or a gaspocket in the build region, but instead the build region remains filledwith the polymerizable liquid throughout the reciprocation steps, andthe gradient of polymerization zone or region remains in contact withthe “dead zone” and with the growing object being fabricated throughoutthe reciprocation steps. As will be appreciated, a purpose of thereciprocation is to speed or enhance the refilling of the build region,particularly where larger build regions are to be refilled withpolymerizable liquid, as compared to the speed at which the build regioncould be refilled without the reciprocation step.

In some embodiments, the advancing step is carried out intermittently ata rate of 1, 2, 5 or 10 individual advances per minute up to 300, 600,or 1000 individual advances per minute, each followed by a pause duringwhich an irradiating step is carried out. It will be appreciated thatone or more reciprocation steps (e.g., upstroke plus downstroke) may becarried out within each advancing step. Stated differently, thereciprocating steps may be nested within the advancing steps.

In some embodiments, the individual advances are carried out over anaverage distance of travel for each advance of from 10 or 50 microns to100 or 200 microns (optionally including the total distance of travelfor each vertically reciprocating step, e.g., the sum of the upstrokedistance minus the downstroke distance).

Apparatus for carrying out the invention in which the reciprocationsteps described herein are implemented substantially as described above,with the drive associated with the carrier, and/or with an additionaldrive operatively associated with the transparent member, and with thecontroller operatively associated with either or both thereof andconfigured to reciprocate the carrier and transparent member withrespect to one another as described above.

VI. Increased Speed of Fabrication by Increased Light Intensity.

In general, it has been observed that speed of fabrication can increasewith increased light intensity. In some embodiments, the light isconcentrated or “focused” at the build region to increase the speed offabrication. This may be accomplished using an optical device such as anobjective lens.

The speed of fabrication may be generally proportional to the lightintensity. For example, the build speed in millimeters per hour may becalculated by multiplying the light intensity in milli Watts per squarecentimeter and a multiplier. The multiplier may depend on a variety offactors, including those discussed below. A range of multiplers, fromlow to high, may be employed. On the low end of the range, themultiplier may be about 10, 15, 20 or 30. On the high end of themutipler range, the multiplier may be about 150, 300, 400 or more.

The relationships described above are, in general, contemplated forlight intensities of from 1, 5 or 10 milliWatts per square centimeter,up to 20 or 50 milliWatts per square centimeter.

Certain optical characteristics of the light may be selected tofacilitate increased speed of fabrication. By way of example, a bandpass filter may be used with a mercury bulb light source to provide365±10 nm light measured at Full Width Half Maximum (FWHM). By way offurther example, a band pass filter may be used with an LED light sourceto provide 375±15 nm light measured at FWHM.

As noted above, polymerizable liquids used in such processes are, ingeneral, free radical polymerizable liquids with oxygen as theinhibitor, or acid-catalyzed or cationically polymerizable liquids witha base as the inhibitor. Some specific polymerizable liquids will ofcourse cure more rapidly or efficiently than others and hence be moreamenable to higher speeds, though this may be offset at least in part byfurther increasing light intensity.

At higher light intensities and speeds, the “dead zone” may becomethinner as inhibitor is consumed. If the dead zone is lost then theprocess will be disrupted. In such case, the supply of inhibitor may beenhanced by any suitable means, including providing an enriched and/orpressurized atmosphere of inhibitor, a more porous semipermeable member,a stronger or more powerful inhibitor (particularly where a base isemployed), etc.

In general, lower viscosity polymerizable liquids are more amenable tohigher speeds, particularly for fabrication of articles with a largeand/or dense cross section (although this can be offset at least in partby increasing light intensity). Polymerizable liquids with viscositiesin the range of 50 or 100 centipoise, up to 600, 800 or 1000 centipoiseor more (as measured at room temperature and atmospheric pressure with asuitable device such as a HYDRAMOTION REACTAVISC™ Viscometer (availablefrom Hydramotion Ltd, 1 York Road Business Park, Malton, York Y017 6YAEngland). In some embodiments, where necessary, the viscosity of thepolymerizable liquid can advantageously be reduced by heating thepolymerizable liquid, as described above.

In some embodiments, such as fabrication of articles with a large and/ordense cross-section, speed of fabrication can be enhanced by introducingreciprocation to “pump” the polymerizable liquid, as described above,and/or the use of feeding the polymerizable liquid through the carrier,as also described above, and/or heating and/or pressurizing thepolymerizable liquid, as also described above.

VII. Tiling.

It may be desirable to use more than one light engine to preserveresolution and light intensity for larger build sizes. Each light enginemay be configured to project an image (e.g., an array of pixels) intothe build region such that a plurality of “tiled” images are projectedinto the build region. As used herein, the term “light engine” can meanan assembly including a light source, a DLP device such as a digitalmicromirror or LCD device and an optical device such as an objectivelens. The “light engine” may also include electronics such as acontroller that is operatively associated with one or more of the othercomponents.

This is shown schematically in FIG. 17A-FIG. 17C. The light engineassemblies 130A, 130B produce adjacent or “tiled” images 140A, 140B. InFIG. 17A, the images are slightly misaligned; that is, there is a gapbetween them. In FIG. 17B, the images are aligned; there is no gap andno overlap between them. In FIG. 17C, there is a slight overlap of theimages 140A and 140B.

In some embodiments, the configuration with the overlapped images shownin FIG. 17C is employed with some form of “blending” or “smoothing” ofthe overlapped regions as generally discussed in, for example, U.S. Pat.Nos. 7,292,207, 8,102,332, 8,427,391, 8,446,431 and U.S. PatentApplication Publication Nos. 2013/0269882, 2013/0278840 and2013/0321475, the disclosures of which are incorporated herein in theirentireties.

The tiled images can allow for larger build areas without sacrificinglight intensity, and therefore can facilitate faster build speeds forlarger objects. It will be understood that more than two light engineassemblies (and corresponding tiled images) may be employed. Variousembodiments of the invention employ at least 4, 8, 16, 32, 64, 128 ormore tiled images.

VIII. Dual Hardening Polymerizable Liquids: Part B.

As noted above, in some embodiments of the invention, the polymerizableliquid comprises a first light polymerizable component (sometimesreferred to as “Part A” herein) and a second component that solidifiesby another mechanism, or in a different manner from, the first component(sometimes referred to as “Part B” herein), typically by furtherreacting, polymerizing, or chain extending. Numerous embodiments thereofmay be carried out. In the following, note that, where particularacrylates such as methacrylates are described, other acrylates may alsobe used.

Part A Chemistry.

As noted above, in some embodiments of the present invention, a resinwill have a first component, termed “Part A.” Part A comprises orconsists of a mixture of monomers and/or prepolymers that can bepolymerized by exposure to actinic radiation or light. This resin canhave a functionality of 2 or higher (though a resin with a functionalityof 1 can also be used when the polymer does not dissolve in itsmonomer). A purpose of Part A is to “lock” the shape of the object beingformed or create a scaffold for the one or more additional components(e.g., Part B). Importantly, Part A is present at or above the minimumquantity needed to maintain the shape of the object being formed afterthe initial solidification. In some embodiments, this amount correspondsto less than ten, twenty, or thirty percent by weight of the total resin(polymerizable liquid) composition.

In some embodiments, Part A can react to form a cross-linked polymernetwork or a solid homopolymer.

Examples of suitable reactive end groups suitable for Part Aconstituents, monomers, or prepolymers include, but are not limited to:acrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffoldin which a second reactive resin component, termed “Part B,” cansolidify during a second step (which may occur concurrently with orfollowing the solidification of Part A). This secondary reactionpreferably occurs without significantly distorting the original shapedefined during the solidification of Part A. Alternative approacheswould lead to a distortion in the original shape in a desired manner.

In particular embodiments, when used in the methods and apparatusdescribed herein, the solidification of Part A is continuously inhibitedduring printing within a certain region, by oxygen or amines or otherreactive species, to form a liquid interface between the solidified partand an inhibitor-permeable film or window (e.g., is carried out bycontinuous liquid interphase/interface printing/production).

Part B Chemistry.

Part B may comprise, consist of or consist essentially of a mix ofmonomers and/or prepolymers that possess reactive end groups thatparticipate in a second solidification reaction after the Part Asolidification reaction. In some embodiments, Part B could be addedsimultaneously to Part A so it is present during the exposure toactinide radiation, or Part B could be infused into the object madeduring the 3D printing process in a subsequent step. Examples of methodsused to solidify Part B include, but are not limited to, contacting theobject or scaffold to heat, water or water vapor, light at a differentwavelength than that at which Part A is cured, catalysts, (with orwithout additional heat), evaporation of a solvent from thepolymerizable liquid (e.g., using heat, vacuum, or a combinationthereof), microwave irradiation, etc., including combinations thereof.

Examples of suitable reactive end group pairs suitable for Part Bconstituents, monomers or prepolymers include, but are not limited to:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate*/hydroxyl, isocyanate*/amine, isocyanate/carboxylic acid,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H(hydrosilylation), Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/Azide (also known as one embodiment of “Click Chemistry,” alongwith additional reactions including thiolene, Michael additions,Diels-Alder reactions, nucleophilic substitution reactions, etc.),alkene/sulfur (polybutadiene vulcanization), alkene/peroxide,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate*/water(polyurethane foams), Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H (tincatalyzed silicone), Si—OH/Si—OH (tin catalyzed silicone),perfluorovinyl (coupling to form perfluorocyclobutane), etc., where*isocyanates include protected isocyanates (e.g., oximes)),diene/dienophiles for Diels-Alder reactions, olefin metathesispolymerization, olefin polymerization using Ziegler-Natta catalysis,ring-opening polymerization (including ring-opening olefin metathesispolymerization, lactams, lactones, siloxanes, epoxides, cyclic ethers,imines, cyclic acetals, etc.), etc.

Other reactive chemistries suitable for Part B will be recognizable bythose skilled in the art. Part B components useful for the formation ofpolymers described in “Concise Polymeric Materials Encyclopedia” and the“Encyclopedia of Polymer Science and Technology” are hereby incorporatedby reference.

Organic Peroxides.

In some embodiments, an organic peroxide may be included in thepolymerizable liquid or resin, for example to facilitate the reaction ofpotentially unreacted double bonds during heat and/or microwaveirradiation curing. Such organic peroxides may be included in the resinor polymerizable liquid in any suitable amount, such as from 0.001 or0.01 or 0.1 percent by weight, up to 1, 2, or 3 percent by weight.Examples of suitable organic peroxides include, but are not limited to,2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (e.g., LUPEROX 101™),dilauroyl peroxide (e.g., LUPEROX LP™), benzoyl peroxide (e.g., LUPEROXA98™), and bis(tert-butyldioxyisopropyl)benzene (e.g., VulCUP R™), etc.,including combinations thereof. Such organic peroxides are availablefrom a variety of sources, including but not limited to Arkema (420 rued'Estienne d'Orves, 92705 Colombes Cedex, France).

Elastomers.

A particularly useful embodiment for implementing the invention is forthe formation of elastomers. Tough, high-elongation elastomers aredifficult to achieve using only liquid UV-curable precursors. However,there exist many thermally cured materials (polyurethanes, silicones,natural rubber) that result in tough, high-elongation elastomers aftercuring. These thermally curable elastomers on their own are generallyincompatible with most 3D printing techniques.

In embodiments of the current invention, small amounts (e.g., less than20 percent by weight) of a low-viscosity UV curable material (Part A)are blended with thermally-curable precursors to form (preferably tough)elastomers (e.g., polyurethanes, polyureas, or copolymers thereof (e.g.,poly(urethane-urea)), and silicones) (Part B). The UV curable componentis used to solidify an object into the desired shape using 3D printingas described herein and a scaffold for the elastomer precursors in thepolymerizable liquid. The object can then be heated after printing,thereby activating the second component, resulting in an objectcomprising the elastomer.

Adhesion of Formed Objects.

In some embodiments, it may be useful to define the shapes of multipleobjects using the solidification of Part A, align those objects in aparticular configuration, such that there is a hermetic seal between theobjects, then activate the secondary solidification of Part B. In thismanner, strong adhesion between parts can be achieved during production.A particularly useful example may be in the formation and adhesion ofsneaker components.

Fusion of Particles as Part B.

In some embodiments, “Part B” may simply consist of small particles of apre-formed polymer. After the solidification of Part A, the object maybe heated above the glass transition temperature of Part B in order tofuse the entrapped polymeric particles.

Evaporation of Solvent as Part B.

In some embodiments, “Part B” may consist of a pre-formed polymerdissolved in a solvent. After the solidification of Part A into thedesired object, the object is subjected to a process (e.g., heat+vacuum)that allows for evaporation of the solvent for Part B, therebysolidifying Part B.

Thermally Cleavable End Groups.

In some embodiments, the reactive chemistries in Part A can be thermallycleaved to generate a new reactive species after the solidification ofPart A. The newly-formed reactive species can further react with Part Bin a secondary solidification. An exemplary system is described byVelankar, Pezos and Cooper, Journal of Applied Polymer Science, 62,1361-1376 (1996). Here, after UV-curing, the acrylate/methacrylategroups in the formed object are thermally cleaved to generateddiisocyanate prepolymers that further react with blended chain-extenderto give high molecular weight polyurethanes/polyureas within theoriginal cured material or scaffold. Such systems are, in general,dual-hardening systems that employ blocked or reactive blockedprepolymers, as discussed in greater detail below. It may be noted thatlater work indicates that the thermal cleavage above is actually adisplacement reaction of the chain extender (usually a diamine) with thehindered urea, giving the final polyurethanes/polyureas withoutgenerating isocyanate intermediates.

Methods of Mixing Components.

In some embodiments, the components may be mixed in a continuous mannerprior to being introduced to the printer build plate. This may be doneusing multi-barrel syringes and mixing nozzles. For example, Part A maycomprise or consist of a UV-curable di(meth)acrylate resin, Part B maycomprise or consist of a diisocyanate prepolymer and a polyol mixture.The polyol can be blended together in one barrel with Part A and remainunreacted. A second syringe barrel would contain the diisocyanate ofPart B. In this manner, the material can be stored without worry of“Part B” solidifying prematurely. Additionally, when the resin isintroduced to the printer in this fashion, a constant time is definedbetween mixing of all components and solidification of Part A.

Other Additive Manufacturing Techniques.

It will be clear to those skilled in the art that the materialsdescribed in the current invention will be useful in other additivemanufacturing techniques including fused deposition modeling (FDM),solid laser sintering (SLS), and ink-jet methods. For example, amelt-processed acrylonitrile-butadiene-styrene resin may be formulatedwith a second UV-curable component that can be activated after theobject is formed by FDM. New mechanical properties could be achieved inthis manner. In another alternative, melt-processed unvulcanized rubberis mixed with a vulcanizing agent such as sulfur or peroxide, and theshape set through FDM, then followed by a continuation of vulcanization.

IX. Dual Hardening Polymerizable Liquids Employing Blocked Constituentsand Thermally Cleavable Blocking Groups.

In some embodiments, where the solidifying and/or curing step (d) iscarried out subsequent to the irradiating step (e.g., by heating ormicrowave irradiating); the solidifying and/or curing step (d) iscarried out under conditions in which the solid polymer scaffolddegrades and forms a constituent necessary for the polymerization of thesecond component (e.g., a constituent such as (i) a prepolymer, (ii) adiisocyanate or polyisocyanate, and/or (iii) a polyol and/or diol, wherethe second component comprises precursors to a polyurethane/polyurearesin). Such methods may involve the use of reactive or non-reactiveblocking groups on or coupled to a constituent of the first component,such that the constituent participates in the first hardening orsolidifying event, and when de-protected (yielding free constituent andfree blocking groups or blocking agents) generates a free constituentthat can participate in the second solidifying and/or curing event.Non-limiting examples of such methods are described further below.

A. Dual Hardening Polymerizable Liquids Employing Blocked Prepolymersand Thermally Cleavable Blocking Groups.

Some “dual cure” embodiments of the present invention are, in general, amethod of forming a three-dimensional object, comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of a blocked or reactiveblocked prepolymer, optionally but in some embodiments preferably areactive diluent, a chain extender, and a photoinitiator;

(c) irradiating the build region with light through the opticallytransparent member to form a (rigid, compressible, collapsible, flexibleor elastic) solid blocked polymer scaffold from the blocked prepolymerand optionally the reactive diluent while concurrently advancing thecarrier away from the build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to, thethree-dimensional object, with the intermediate containing the chainextender; and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form the three-dimensional product from thethree-dimensional intermediate (without wishing to be bound to anyparticular mechanism, the heating or microwave irradiating may cause thechain extender to react with the blocked or reactive blocked prepolymeror an unblocked product thereof).

In some embodiments, the blocked or reactive blocked prepolymercomprises a polyisocyanate.

In some embodiments, the blocked or reactive blocked prepolymercomprises a compound of the formula A-X-A, where X is a hydrocarbylgroup and each A is an independently selected substituent of Formula X:

where R is a hydrocarbyl group, R′ is O or NH, and Z is a blockinggroup, the blocking group optionally having a reactive terminal group(e.g., a polymerizable end group such as an epoxy, alkene, alkyne, orthiol end group, for example an ethylenically unsaturated end group suchas a vinyl ether). In a particular example, each A is an independentlyselected substituent of Formula (XI):

where R and R′ are as given above.

In some embodiments, the blocked or reactive blocked prepolymercomprises a polyisocyanate oligomer produced by the reaction of at leastone diisocyanate (e.g., a diisocyanate such as hexamethylenediisocyanate (HDI), bis-(4-isocyanatocyclohexyl)methane (HMDI),isophorone diisocyanate (IPDI), etc., a triisocyanate, etc.) with atleast one polyol (e.g., a polyether or polyester or polybutadiene diol).

In some embodiments, the reactive blocked prepolymer is blocked byreaction of a polyisocyanate with an amine (meth)acrylate monomerblocking agent (e.g., tertiary-butylaminoethyl methacrylate (TBAEMA),tertiary pentylaminoethyl methacrylate (TPAEMA), tertiaryhexylaminoethyl methacrylate (THAEMA), tertiary-butylaminopropylmethacrylate (TBAPMA), acrylate analogs thereof, and mixtures thereof(see, e.g., US Patent Application Publication No. 20130202392). Notethat all of these can be used as diluents as well.

There are many blocking agents for isocyanate. In preferred embodimentsof the current invention, the blocking agent (e.g., TBAEMA) cures (e.g.,from the actinic radiation or light) into the system. Those skilled inthe art can couple (meth)acrylate groups to known blocking agents tocreate additional blocking agents that can be used to carry out thepresent invention. Still further, those skilled in the art can usemaleimide, or substitute maleimide on other known blocking agents, foruse in the present invention.

Examples of known blocking agents which can be substituted on orcovalently coupled to (meth)acrylate or maleimide for use in the presentinvention include, but are not limited to, phenol type blocking agents(e.g., phenol, cresol, xylenol, nitrophenol, chlorophenol, ethyl phenol,t-butylphenol, hydroxy benzoic acid, hydroxy benzoic acid esters,2,5-di-t-butyl-4-hydroxy toluene, etc.), lactam type blocking agents(e.g., ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam,etc.), active methylene type blocking agents (e.g., diethyl malonate,dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, etc.), alcohol type blocking agents (e.g., methanol, ethanol,n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amylalcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,propylene glycol monomethyl ether, methoxyethanol, glycolic acid,glycolic acid esters, lactic acid, lactic acid ester, methylol urea,methylol melamine, diacetone alcohol, ethylene chlorohydrine, ethylenebromohydrine, 1,3-dichloro-2-propanol, ω-hydroperfluoro alcohol,acetocyanhydrine, etc.), mercaptan type blocking agents (e.g., butylmercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan,2-mercapto-benzothiazole, thiophenol, methyl thiophenol, ethylthiophenyl, etc.), acid amide type blocking agents (e.g., acetoanilide,acetoanisidine amide, acrylamide, methacrylamide, acetic amide, stearicamide, benzamide, etc.), imide type blocking agents (e.g., succinimide,phthalimide, maleimide, etc.), amine type blocking agents (e.g.,diphenylamine, phenylnaphthylamine, xylidine, N-phenyl xylidine,carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine, etc.), imidazole type blocking agents (e.g., imidazole,2-ethylimidazole, etc.), urea type blocking agents (e.g., urea,thiourea, ethylene urea, ethylene thiourea, 1,3-diphenyl urea, etc.),carbamate type blocking agents (e.g., N-phenyl carbamic acid phenylester, 2-oxazolidone, etc.), imine type blocking agents (e.g., ethyleneimine, etc.), oxime type blocking agents (e.g., formaldoxime,acetaldoximine, acetoxime, methylethyl ketoxime, diacetylomonoxime,benzophenoxime, cyclohexanonoxime, etc.) and sulfurous acid salt typeblocking agents (e.g., sodium bisulfite, potassium bisulfite, etc.). Ofthese, use is preferably made of the phenol type, the lactam type, theactive methylene type and the oxime type blocking agents (see, e.g.,U.S. Pat. No. 3,947,426).

In some embodiments, the diisocyanate or isocyanate-functional oligomeror prepolymer is blocked with an aldehyde blocking agent, such as aformyl blocking agent. Examples include but are not limited to2-formyloxyethyl (meth)acrylate (FEMA) (or other aldehyde-containingacrylate or methacrylate) with a diisocyanate or isocyanate functionaloligomer or polymer. See, e.g., X. Tassel et al., A New Blocking Agentof isocyanates, European Polymer Journal 36(9), 1745-1751 (2000); T.Haig, P. Badyrka et al., U.S. Pat. No. 8,524,816; and M. Sullivan and D.Bulpett, U.S. Pat. Appl. Pub. No. US20120080824 The reaction product ofsuch an aldehyde blocking agent and an isocyanate can in someembodiments possess an advantage over TBAEMA blocked ABPUs by reducinghydrogen bonding due to urea formation, in turn (in some embodiments)resulting in lower viscosity blocked isocyanates. In addition, in someembodiments, a second advantage is eliminating free amines within thefinal product (a product of the deblocking of TBAEMA from the ABPU)which might oxidize and cause yellowness or lead to degradation.

In some embodiments, the reactive diluent comprises an acrylate, amethacrylate, a styrene, an acrylic acid, a vinylamide, a vinyl ether, avinyl ester (including derivatives thereof), polymers containing any oneor more of the foregoing, and combinations of two or more of theforegoing (e.g., acrylonitrile, styrene, divinyl benzene, vinyl toluene,methyl acrylate, ethyl acrylate, butyl acrylate, methyl (meth)acrylate,amine (meth)acrylates as described above, and mixtures of any two ormore of these). See, e.g., US Patent Application Publication No.20140072806.

In some embodiments, the chain extender comprises at least one diol,diamine or dithiol chain extender (e.g., ethylene glycol,1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol,1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, the correspondingdiamine and dithiol analogs thereof, lysine ethyl ester, arginine ethylester, p-alanine-based diamine, and random or block copolymers made fromat least one diisocyanate and at least one diol, diamine or dithiolchain extender; see, e.g., US Patent Application Publication No.20140010858). Note also that, when dicarboxylic acid is used as thechain extender, polyesters (or carbamate-carboxylic acid anhydrides) aremade.

In some embodiments, the polymerizable liquid comprises:

from 5 or 20 or 40 percent by weight to 60 or 80 or 90 percent by weightof the blocked or reactive blocked prepolymer;

from 10 or 20 percent by weight to 30 or 40 or 50 percent by weight ofthe reactive diluent;

from 5 or 10 percent by weight to 20 or 30 percent by weight of thechain extender; and

from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent by weight of thephotoinitiator. Optional additional ingredients, such as dyes, fillers(e.g., silica), surfactants, etc., may also be included, as discussed ingreater detail above.

An advantage of some embodiments of the invention is that, because thesepolymerizable liquids do not rapidly polymerize upon mixing, they may beformulated in advance, and the filling step carried out by feeding orsupplying the polymerizable liquid to the build region from a singlesource (e.g., a single reservoir containing the polymerizable liquid inpre-mixed form), thus obviating the need to modify the apparatus toprovide separate reservoirs and mixing capability.

Three-dimensional objects made by the process are, in some embodiments,collapsible or compressible (that is, elastic (e.g., has a Young'smodulus at room temperature of from about 0.001, 0.01 or 0.1 gigapascalsto about 1, 2 or 4 gigapascals, and/or a tensile strength at maximumload at room temperature of about 0.01, 0.1, or 1 to about 50, 100, or500 megapascals, and/or a percent elongation at break at roomtemperature of about 10, 20 50 or 100 percent to 1000, 2000, or 5000percent, or more).

An additional example of the preparation of a blocked reactiveprepolymer is shown in the Scheme below:

One can use similar chemistry to that described above to form a reactiveblocked diioscyanate, a reactive blocked chain extender, or a reactiveblocked prepolymer.

A non-limiting example of a dual cure system employing a thermallycleavable end group is shown in the FIG. 25A and the Scheme below:

Without wishing to be bound to any underlying mechanism, in someembodiments, during thermal cure, blocking agent is cleaved anddiisocyanate prepolymer is re-formed and quickly reacts with chainextenders or additional soft segment to form thermoplastic or thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), as follows:

Alternative mechanisms such as those described in section B below mayalso be implemented or involved.

In the scheme above, the dual cure resin is comprised of a UV-curable(meth)acrylate blocked polyurethane (ABPU), a reactive diluent, aphotoinitiator, and a chain extender(s). The reactive diluent (10-50 wt%) is an acrylate or methacrylate that helps to reduce the viscosity ofABPU and will be copolymerized with the ABPU under UV irradiation. Thephotoinitiator (generally about 1 wt %) can be one of those commonlyused UV initiators, examples of which include but are not limited tosuch as acetophenones (diethoxyacetophenone for example), phosphineoxides diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide,phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (PPO), Irgacure 369,etc.

After UV curing to form an intermediate shaped product having blockedpolyurethane oligomers as a scaffold, and carrying the chain extender,the ABPU resin is subjected to a thermal cure, during which a highmolecular weight polyurethane/polyurea is formed by a spontaneousreaction between the polyurethane/polyurea oligomers and the chainextender(s). The polyurethane/polyurea oligomer can react with properchain extenders through substitution of TBAEMA, N-vinylformamide (NVF)or the like by proper chain extenders, either by deblocking ordisplacement. The thermal cure time needed can vary depending on thetemperature, size, shape, and density of the product, but is typicallybetween 1 to 6 hours depending on the specific ABPU systems, chainextenders and temperature.

One advantageous aspect of the foregoing is using a tertiaryamine-containing (meth)acrylate (e.g., t-butylaminoethyl methacrylate,TBAEMA) to terminate synthesized polyurethane/polyurea oligomers withisocyanate at both ends. Using acrylate or methacrylate containinghydroxyl groups to terminate polyurethane/polyurea oligomers withisocyanate ends is used in UV curing resins in the coating field. Theformed urethane bonds between the isocyanate and hydroxyl groups aregenerally stable even at high temperatures. In embodiments of thepresent invention, the urea bond formed between the tertiary amine ofTBAEMA and isocyanate of the oligomer becomes labile when heated tosuitable temperature (for example, about 100° C.), regenerating theisocyanate groups that will react with the chain extender(s) duringthermal-cure to form high molecular weight polyurethane (PU). While itis possible to synthesize other (meth)acrylate containing isocyanateblocking functionality as generally used (such as N-vinylformamide,s-caprolactam, 1,2,3-triazole, methyl ethyl ketoxime, diethyl malonate,etc.), the illustrative embodiment uses TBAEMA that is commerciallyavailable. The used chain extenders can be diols, diamines, triols,triamines, or their combinations, or others. Ethylene glycol,1,4-butanediol, methylene dicyclohexylamine (H12MDA; or PACM as thecommercial name from Air Products), hydroquinone bis(2-Hydroxyethyl)Ether (HQEE), 4,4′-Methylenebis(3-Chloro-2,6-Diethylaniline) (MCDEA),4,4′-methylene-bis-(2,6 diethylaniline)(MDEA),4,4′-Methylenebis(2-chloroaniline) (MOCA) are the preferred chainextenders.

To produce an ABPU, TBAEMA may be used to terminate the isocyanate endgroups of the prepolymer, which is derived from isocyanate tippedpolyols. The polyols (preferably with hydroxyl functionality of 2) usedcan be polyethers (especially polytetramethylene oxide (PTMO),polypropylene glycol (PPG)), polyesters (polycaprolactone (PCL),polycarbonate, etc.), polybutadiene and block copolymers such as PCL andPTMO block copolymer (Capa 7201A of Perstop, Inc.). The molecular weightof these polyols can be 500 to 6000 Da, and 500-2000 Da are preferred.In the presence of a catalyst (e.g., stannous octoate with 0.1-0.3 wt %to the weight of polyol; other tin catalysts or amine catalysts),diisocyanate (e.g., toluene diisocyanate (TDI), methylene diphenyldiisocyanate (MDI), hexamethylene diisocyanate (HDI), isophoronediisocyanate (IPDI), hydrogenated MDI (HMDI), para-phenyl diisocyanate(PPDI) etc.) is added to the polyol (or the reverse order; preferablythe polyol being added to the isocyanate) with certain molar ratio(larger than 1:1; preferably, no less than 2:1, and 2:1 is mostlypreferred) to make a prepolymer with residual isocyanate groups (50-100°C.). TBAEMA is then added to the reaction [Note:moles(TBAEMA)*2+moles(OH)=moles(isocyanate)] to cap the remainingisocyanate groups, resulting in ABPU (under 40-70° C.). Radicalinhibitors such as hydroquinone (100-500 ppm) can be used to inhibitpolymerization of (meth)acrylate during the reaction.

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject, or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups, it will be appreciated that unreactiveblocking groups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used toform three-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

B. Dual Hardening Polymerizable Liquids Employing Blocked Diisocyanatesand Thermally Cleavable Blocking Groups.

Another embodiment provides a method of forming a three-dimensionalobject comprised of polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), the method comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of (i) a blocked or reactiveblocked diisocyanate, (ii) a polyol and/or polyamine, (iii) a chainextender, (iv) a photoinitiator, and (v) optionally but in someembodiments preferably a reactive diluent (vi) optionally but in someembodiments preferably a pigment or dye, (vii) optionally but in someembodiments preferably a filler (e.g., silica),

(c) irradiating the build region with light through the opticallytransparent member to form a solid blocked diisocyanate scaffold fromthe blocked diisocyanate, and optionally the reactive diluent, andadvancing the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object, with the intermediatecontaining the chain extender and polyol and/or polyamine; and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently (e.g., sufficiently to de-block the blocked diisocyanateand form an unblocked diisocyanate that, in turn, polymerizes with thechain extender and polyol and/or polyamine) to form thethree-dimensional product comprised of polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), from thethree-dimensional intermediate.

In some embodiments, the blocked or reactive blocked diisocyanatecomprises a compound of the formula A′-X′-A′, where X′ is a hydrocarbylgroup and each A′ is an independently selected substituent of Formula(X′):

where Z is a blocking group, the blocking group optionally having areactive terminal group (e.g., a polymerizable end group such as anepoxy, alkene, alkyne, or thiol end group, for example an ethylenicallyunsaturated end group such as a vinyl ether). In a particular example,each A′ is an independently selected substituent of Formula (XI′):

Other constituents and steps of these methods are carried out in likemanner as described in section IX.A. above.

In a non-limiting example, a blocked diisocyanate is prepared as shownin the Scheme below. Such blocked diisocyanates may be used in methodsas shown in FIG. 25B.

Without wishing to be bound by any particular underlying mechanism, insome embodiments, during thermal cure, the blocking agent is cleaved andthe chain extender reacts to form thermoplastic or thermosetpolyurethane, polyurea, or a copolymer thereof (e.g.,poly(urethane-urea)), for example as shown below:

In an alternative mechanism, the chain extender reacts with the blockeddiisocyante, eliminates the blocking agent, in the process formingthermoplastic or thermoset polyurethane, polyurea, or a copolymerthereof (e.g., poly(urethane-urea)).

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups, it will be appreciated that unreactiveblocking groups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used toform three-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

C. Dual Hardening Polymerizable Liquids Employing Blocked ChainExtenders and Thermally Cleavable Blocking Groups.

Another embodiment provides a method of forming a three-dimensionalobject comprised of polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), the method comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of (i) a polyol and/orpolyamine, (ii) a blocked or reactive blocked diisocyanate chainextender, (iii) optionally one or more additional chain extenders, (iv)a photoinitiator, and (v) optionally but in some embodiments preferablya reactive diluent (vi) optionally but in some embodiments preferably apigment or dye, (vii) optionally but in some embodiments preferably afiller (e.g., silica);

(c) irradiating the build region with light through the opticallytransparent member to form a solid blocked chain diisocyanate chainextender scaffold from the blocked or reactive blocked diisocyanatechain extender and optionally the reactive diluent, and advancing thecarrier away from the build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to, thethree-dimensional object, with the intermediate containing the polyoland/or polyamine and optionally one or more additional chain extenders;and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form the three-dimensional product comprised ofpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), from the three-dimensional intermediate (e.g.,heating or microwave irradiating sufficiently to de-block the blockeddiisocyanate chain extender to form an unblocked diisocyanate chainextender that, in turn, polymerizes with the polyol and/or polyamine andoptionally one or more additional chain extenders).

In some embodiments, the blocked or reactive blocked diisocyanate chainextender comprises a compound of the formula A″-X″-A″, where X″ is ahydrocarbyl group, and each A″ is an independently selected substituentof Formula (X″):

where R is a hydrocarbyl group, R′ is O or NH, and Z is a blockinggroup, the blocking group optionally having a reactive terminal group(e.g., a polymerizable end group such as an epoxy, alkene, alkyne, orthiol end group, for example an ethylenically unsaturated end group suchas a vinyl ether). In a particular example, each A″ is an independentlyselected substituent of Formula (XI″):

where R and R′ are as given above.

Other constituents and steps employed in carrying out these methods maybe the same as described in section IX.A. above.

An example of the preparation of a blocked diol chain extender is shownin the Scheme below.

An example of the preparation of a blocked diamine chain extender isshown in the Scheme below:

An example of method of the present invention carried out with thematerials above is given in FIG. 25C.

Without wishing to be bound to any underlying mechanism of theinvention, in some embodiments, during thermal cure, (a) the blockedisocyanate-capped chain extender reacts either directly with softsegment and/or chain extender amine or alcohol groups, displacing theblocking agent; or (b) the blocked isocyanate-capped chain extender iscleaved and diisocyanate-capped chain extender is re-formed and reactswith soft segments and additional chain extender if necessary to yieldthermoplastic or thermoset polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)), such as follows:

An alternative mechanism analogous to that described in section IX.B.above may also be implemented or employed.

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups (that is, blocking groups containingpolymerizable moieties), it will be appreciated that unreactive blockinggroups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used toform three-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

Those skilled in the art will appreciate that systems as described inYing and Cheng, Hydrolyzable Polyureas Bearing Hindered Urea Bonds, JACS136, 16974 (2014), may be used in carrying out the methods describedherein.

X. Articles Comprised of Interpenetrating Polymer Networks (IPNs) Formedfrom Dual Hardening Polymerizable Liquids.

In some embodiments, polymerizable liquids comprising dual hardeningsystems such as described above are useful in forming three-dimensionalarticles that, in turn, comprise interpenetrating polymer networks. Thisarea has been noted by Sperling at Lehigh University and K. C. Frisch atthe University of Detroit, and others.

In non-limiting examples, the polymerizable liquid and method steps areselected so that the three-dimensional object comprises the following:

Sol-Gel compositions. This may be carried out with an amine (ammonia)permeable window or semipermeable member. In the system discussed here,tetraethyl orthosiliciate (TEOS), epoxy (diglycidyl ether of BisphenolA), and 4-amino propyl triethoxysilane may be added to a free radicalcrosslinker, and in the process the free radical crosslinker polymerizesand contains the noted reactants, which are then reacted in another stepor stage. Reaction requires the presence of water and acid. Photoacidgenerators (PAGs) could optionally be added to the mixture describedabove to promote the reaction of the silica based network. Note that ifonly TEOS is included, one will end up with a silica (glass) network.One could then increase the temperature to remove the organic phase andbe left with a silica structure that would be difficult to prepare bymore conventional methods. Many variations (different polymericstructures) can be prepared by this process in addition to epoxiesincluding urethanes, functionalized polyols, silicone rubber, etc.

Hydrophobic-hydrophilic IPNs. Prior IPN research contained a number ofexamples for hydrophobic-hydrophilic networks for improved bloodcompatibility as well as tissue compatibility for biomedical parts.Poly(hydroxyethyl (meth)acrylate) is a typical example of a hydrophiliccomponent. Another option is to add poly(ethylene oxide) polyols orpolyamines with a diisocyanate to produce polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), incorporated in thereactive system.

Phenolic resins (resoles). Precursors to phenolic resins involve eitherphenolic resoles (formaldehyde terminal liquid oligomers) or phenolicnovolacs (phenol terminal solid oligomers crosslinkable withhexamethyltetraamine). For the present process phenolic resoles can beconsidered. The viscosity thereof may be high but dilution with alcohols(methanol or ethanol) may be employed. Combination of the phenolicresole with the crosslinkable monomer can then provide a product formedfrom an IPN. Reaction of the phenolic resole to a phenolic resin canoccur above 100° C. in a short time range. One variation of thischemistry would be to carbonize the resultant structure to carbon orgraphite. Carbon or graphite foam is typically produced from phenolicfoam and used for thermal insulation at high temperatures.

Polyimides. Polyimides based on dianhydrides and diamines are amenableto the present process. In this case the polyimide monomers incorporatedinto the reactive crosslinkable monomer are reacted to yield an IPNstructure. Most of the dianhydrides employed for polyimides may becrystalline at room temperature but modest amounts of a volatile solventcan allow a liquid phase. Reaction at modest temperatures (e.g., in therange of about 100° C.) is possible to permit polyimide formation afterthe network is polymerized.

Conductive polymers. The incorporation of aniline and ammoniumpersulfate into the polymerizable liquid is used to produce a conductivepart. After the reactive system is polymerized and a post treatment withacid (such as HCl vapor), polymerization to polyaniline can thencommence.

Natural product based IPNs. Numerous natural product based IPNs areknown based on triglyceride oils such as castor oil. These can beincorporated into the polymerizable liquid along with a diisocyanate.Upon completion of the part the triglycerides can then be reacted withthe diisocyanate to form a crosslinked polyurethane. Glycerol can ofcourse also be used.

Sequential IPNs. In this case, the molded crosslinked networks areswollen with a monomer and free radical catalyst (peroxide) andoptionally crosslinker followed by polymerization. The crosslinkedtriacylate system should imbide large amounts of styrene, acrylateand/or methacrylate monomers allowing a sequential IPN to be produced.

Polyolefin polymerization. Polyolefin catalysts (e.g., metallocenes) canbe added to the crosslinkable reactive system. Upon exposure of the partto pressurized ethylene (or propylene) or a combination (to produce EPRrubber) and temperature (in the range of 100° C.) the part can thencontain a moderate to substantial amount of the polyolefin. Ethylene,propylene and alpha olefin monomers should easily diffuse into the partto react with the catalyst at this temperature, and as polymerizationproceeds more olefin will diffuse to the catalyst site. A large numberof parts can be post-polymerized at the same time.

XI. Fabrication Products.

A. Example Three-Dimensional (3D) Objects.

Three-dimensional products produced by the methods and processes of thepresent invention may be final, finished or substantially finishedproducts, or may be intermediate products for which furthermanufacturing steps such as surface treatment, laser cutting, electricdischarge machining, etc., is intended. Intermediate products includeproducts for which further additive manufacturing, in the same or adifferent apparatus, may be carried out. For example, a fault orcleavage line may be introduced deliberately into an ongoing “build” bydisrupting, and then reinstating, the gradient of polymerization zone,to terminate one region of the finished product, or simply because aparticular region of the finished product or “build” is less fragilethan others.

Numerous different products can be made by the methods and apparatus ofthe present invention, including both large-scale models or prototypes,small custom products, miniature or microminiature products or devices,etc. Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,functional structures, microneedle arrays, fibers and rods such aswaveguides, micromechanical devices, microfluidic devices, etc.

Thus in some embodiments the product can have a height of from 0.1 or 1millimeters up to 10 or 100 millimeters, or more, and/or a maximum widthof from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more. Inother embodiments, the product can have a height of from 10 or 100nanometers up to 10 or 100 microns, or more, and/or a maximum width offrom 10 or 100 nanometers up to 10 or 100 microns, or more. These areexamples only; maximum size and width depends on the architecture of theparticular device and the resolution of the light source and can beadjusted depending upon the particular goal of the embodiment or articlebeing fabricated.

In some embodiments, the ratio of height to width of the product is atleast 2:1, 10:1, 50:1, or 100:1, or more, or a width to height ratio of1:1, 10:1, 50:1, or 100:1, or more.

In some embodiments, the product has at least one, or a plurality of,pores or channels formed therein, as discussed further below.

The processes described herein can produce products with a variety ofdifferent properties. Hence in some embodiments the products are rigid;in other embodiments the products are flexible or resilient. In someembodiments, the products are a solid; in other embodiments, theproducts are a gel such as a hydrogel. In some embodiments, the productshave a shape memory (that is, return substantially to a previous shapeafter being deformed, so long as they are not deformed to the point ofstructural failure). In some embodiments, the products are unitary (thatis, formed of a single polymerizable liquid); in some embodiments, theproducts are composites (that is, formed of two or more differentpolymerizable liquids). Particular properties will be determined byfactors such as the choice of polymerizable liquid(s) employed.

In some embodiments, the product or article made has at least oneoverhanging feature (or “overhang”), such as a bridging element betweentwo supporting bodies, or a cantilevered element projecting from onesubstantially vertical support body. Because of the unidirectional,continuous nature of some embodiments of the present processes, theproblem of fault or cleavage lines that form between layers when eachlayer is polymerized to substantial completion and a substantial timeinterval occurs before the next pattern is exposed, is substantiallyreduced. Hence, in some embodiments the methods are particularlyadvantageous in reducing, or eliminating, the number of supportstructures for such overhangs that are fabricated concurrently with thearticle.

B. Example Structures and Geometries of 3D Objects.

In example embodiments, the three-dimensional (3D) object may be formedwith thousands or millions of shape variations imparted on thethree-dimensional object while being formed. In example embodiments, thepattern generator generates different patterns of light to activatephotoinitiator in the region of the gradient of polymerization to impartdifferent shapes as the object is extracted through the gradient ofpolymerization. In example embodiments, the pattern generator may havehigh resolution with millions of pixel elements that can be varied tochange the shape that is imparted. For example, the pattern generatormay be a DLP with more than 1,000 or 2,000 or 3,000 or more rows and/ormore than 1,000 or 2,000 or 3,000 or more columns of micromirrors, orpixels in an LCD panel, that can be used to vary the shape. As a result,very fine variations or gradations may be imparted on the object alongits length. In example embodiments, this allows complexthree-dimensional objects to be formed at high speed with asubstantially continuous surface without cleavage lines or seams. Insome examples, more than a hundred, thousand, ten thousand, hundredthousand or million shape variations may be imparted on thethree-dimensional object being formed without cleavage lines or seamsacross a length of the object being formed of more than 1 mm, 1 cm, 10cm or more or across the entire length of the formed object. In exampleembodiments, the object may be continuously formed through the gradientof polymerization at a rate of more than 1, 10, 100, 1000, 10000 or moremicrons per second.

In example embodiments, this allows complex three-dimensional (3D)objects to be formed. In some example embodiments, the 3D formed objectshave complex non-injection moldable shapes. The shapes may not becapable of being readily formed using injection molding or casting. Forexample, the shapes may not be capable of being formed by discrete moldelements that are mated to form a cavity in which fill material isinjected and cured, such as a conventional two-part mold. For example,in some embodiments, the 3D formed objects may include enclosed cavitiesor partially open cavities, repeating unit cells, or open-cell orclosed-cell foam structures that are not amenable to injection moldingand may including hundreds, thousands or millions of these structures orinterconnected networks of these structures. However, in exampleembodiments, these shapes may be 3D formed using the methods describedin the present application with a wide range of properties, including awide range of elastomeric properties, tensile strength and elongation atbreak through the use of dual cure materials and/or interpenetratingpolymer networks to form these structures. In example embodiments, the3D objects may be formed without cleavage lines, parting lines, seams,sprue, gate marks or ejector pin marks that may be present withinjection molding or other conventional techniques. In some embodiments,the 3D formed objects may have continuous surface texture (whethersmooth, patterned or rough) that is free from molding or other printingartifacts (such as cleavage lines, parting lines, seams, sprue, gatemarks or ejector pin marks) across more than 1 mm, 1 cm, 10 cm or moreor across the entire length of the formed object. In exampleembodiments, complex 3D objects may be formed with no discrete layersvisible or readily detectable from the printing process in the finished3D object across more than 1 mm, 1 cm, 10 cm or more or across theentire length of the formed object. For example, the varying shapesimparted during the course of printing by the pattern generator may notbe visible or detectable as different layers in the finished 3D objectsince the printing occurs through the gradient of polymerization zone(from which the 3D object is extracted as it is exposed by varyingpatterns projected from the pattern generator). While the 3D objectsresulting from this process may be referred to as 3D printed objects,the 3D objects may be formed through continuous liquid interphaseprinting without the discrete layers or cleavage lines associated withsome 3D printing processes.

In some embodiments, the 3D formed object may include one or morerepeating structural elements to form the 3D objects, including, forexample, structures that are (or substantially correspond to) enclosedcavities, partially-enclosed cavities, repeating unit cells or networksof unit cells, foam cell, Kelvin foam cell or other open-cell orclosed-cell foam structures, crisscross structures, overhang structures,cantilevers, microneedles, fibers, paddles, protrusions, pins, dimples,rings, tunnels, tubes, shells, panels, beams (including I-beams,U-beams, W-beams and cylindrical beams), struts, ties, channels (whetheropen, closed or partially enclosed), waveguides, triangular structures,tetrahedron or other pyramid shape, cube, octahedron, octagon prism,icosidodecahedron, rhombic triacontahedron or other polyhedral shapes ormodules (including Kelvin minimal surface tetrakaidecahedra, prisms orother polyhedral shapes), pentagon, hexagonal, octagon and other polygonstructures or prisms, polygon mesh or other three-dimensional structure.In some embodiments, a 3D formed object may include combinations of anyof these structures or interconnected networks of these structures. Inexample embodiments, all or a portion of the structure of the 3D formedobject may correspond (or substantially correspond) to one or moreBravais lattice or unit cell structures, including cubic (includingsimple, body-centered or face-centered), tetragonal (including simple orbody-centered), monoclinic (including simple or end-centered),orthorhombic (including simple, body-centered, face-centered orend-centered), rhombohedral, hexagonal and triclinic structures. Inexample embodiments, the 3D formed object may include shapes or surfacesthat correspond (or substantially correspond) to a catenoid, helicoid,gyroid or lidinoid, other triply periodic minimal surface (TPMS), orother geometry from the associate family (or Bonnet family) or Schwarz P(“Primitive”) or Schwarz D (“Diamond”), Schwarz H (“Hexagonal”) orSchwarz CLP (“Crossed layers of parallels”) surfaces, argyle or diamondpatterns, lattice or other pattern or structure.

In example embodiments, the pattern generator may be programmed to varyrapidly during printing to impart different shapes into the gradient ofpolymerization with high resolution. As a result, any of the abovestructural elements may be formed with a wide range of dimensions andproperties and may be repeated or combined with other structuralelements to form the 3D object. In example embodiments, the 3D formedobject may include a single three-dimensional structure or may includemore than 1, 10, 100, 1000, 10000, 100000, 1000000 or more of thesestructural elements. The structural elements may be repeated structuralelements of similar shapes or combinations of different structuralelements and can be any of those described above or other regular orirregular shapes. In example embodiments, each of these structuralelements may have a dimension across the structure of at least 10nanometers, 100 nanometers, microns, 100 microns, 1 mm, 1 cm, 10 cm, 50cm or more or may have a dimension across the structure of less than 50cm, 10 cm, 1 cm, 1 mm, 100 microns, 10 microns, 100 nanometers or 10nanometers or less. In example embodiments, a height, width or otherdimension across the structure may be in the range of from about 10nanometers to about 50 cm or more or any range subsumed therein. As usedherein, “any range subsumed therein” means any range that is within thestated range. For example, the following are all subsumed within therange of about 10 nanometers to about 50 square cm and are includedherein: 10 nanometers to 1 micron; 1 micron to 1 millimeter; 1millimeter to 1 centimeter; and 1 centimeter to 50 cm or any other rangeor set of ranges within the stated range. In example embodiments, eachof the structural elements may form a volume of the 3D object in therange of from about 10 square nanometers to about 50 square cm or moreor any range subsumed therein. In example embodiments, each of thestructural elements may form a cavity or hollow region or gap betweensurfaces of the structural element having a dimension across the cavityor hollow region or gap in the range of from about nanometers to about50 cm or more or any range subsumed therein or may define a volumewithin the expanse of the 3D formed object in the range of from about 10square nanometers to about 50 square cm or more or any range subsumedtherein.

The structural elements may be about the same size or the size may varythroughout the volume of the 3D formed object. The sizes may increase ordecrease from one side of the 3D formed object to another side(gradually or step-wise) or elements of different shapes may beintermixed in regular or irregular patterns (for example, a 3Delastomeric foam with varying sizes of open-cell and/or closed-cellcavities intermixed throughout the foam).

In some embodiments, the 3D formed objects may have irregular shapeswith overhangs, bridging elements or asymmetries or may otherwise havean offset center of gravity in the direction being formed. For example,the 3D formed object may be asymmetric. In example embodiments, the 3Dformed object may not have rotational symmetry around any axis or mayhave rotational symmetry only around a single axis. In exampleembodiments, the 3D formed object may not have reflectional symmetryaround any plane through the 3D formed object or may have reflectionalsymmetry only around a single plane. In example embodiments, the 3Dobject may have an offset center of gravity. For example, the center ofgravity of the 3D formed object may not be at the positional center ofthe object. In some examples, the center of gravity may not be locatedalong any central axis of the object. For example, the 3D formed objectmay be a shoe sole or insert that generally follows the contour of afoot. The shoe sole or insert may tilt to the right or left and havedifferent widths for the heel and toes. As a result, the 3D formedobject in this example will not have reflectional symmetry from side toside or front to back. However, it may have reflectional symmetry frombottom to top if it is a uniformly flat shoe sole or insert. In otherexamples, the shoe sole or insert may be flat on one side and becontoured to receive the arch of a foot on the other side and, as aresult, will not have reflectional symmetry from bottom to top either.Other 3D formed objects for wearable, prosthetic or anatomical shapes ordevices may have similar asymmetries and/or offset center of gravity.For example, a 3D formed object for a dental mold or dental implant maysubstantially conform to the shape of a tooth and may not havereflectional symmetry about any plane. In another example, a 3D formedcomponent for a wearable device may substantially conform to the shapeof a body party and have corresponding asymmetries, such as athleticwear such as a right or left contoured shin guard or foam padding orinsert for use between a hard shin guard or a helmet or other wearablecomponent and the human body. These are examples only and any number of3D formed objects may be asymmetric and/or have an offset center ofgravity. In example embodiments, where there are significant asymmetriesor protruding elements (such as arms, bridging elements, cantilevers,brush fibers or the like) and the desired structural elements will beelastomeric, there is a potential for deformation during 3D printing orsubsequent curing. For example, if a large amount of non-UV curableelastomeric resin material is included, gravity may cause deformationbefore final curing. While the scaffold formed from UV-curable materialduring 3D printing (from the initial cure in a dual cure process) helpslock-in the shape, some elastomeric compositions with highly asymmetricor protruding shapes may be susceptible to deformation. In some exampleembodiments, the UV curable material in the composition may be adjustedto form a more rigid scaffold to avoid deformation. In other exampleembodiments, objects with asymmetric shapes and/or offset center ofgravity may be formed in pairs (or in other combinations) withconnectors that are later removed, particularly if the 3D formed objectsor protruding elements are relatively long. In an example, anelastomeric 3D object may be formed along a length, and have anasymmetry, center of gravity offset and/or protruding element transverseto the length that is more than 10%, 20%, 30%, 40%, 50% or more of thelength. For example, the 3D formed object may have a length of about 1cm to 50 cm or more or any range subsumed therein and may have atransverse or lateral asymmetry or protruding element of about 1 cm to50 cm or more or any range subsumed therein. In an example embodiment,two or more of these objects may be formed together in a way thatprovides support for the transverse or protruding elements until theelastomeric material is cured and the objects are separated. Forexample, two shoe soles may be formed (e.g., when formed in thedirection of their length) as a pair (for example, with rotated andinverted shoe soles formed together with small removable connectorsbetween them) such that the soles provide support to one another whilebeing formed. In other example embodiments, other support structures maybe formed and removed after curing of the elastomeric material.

C. Example Materials and Compositions of 3D Objects.

In example embodiments, 3D formed objects may have any of the aboveshapes or structures and may comprise or consist of or consistessentially of: (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), and/or (iii) combinations thereof (optionallyblended with de-blocked blocking group which is copolymerized with thereactive diluents(s), for example as an interpenetrating polymernetwork, a semi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network), and/or (iv) photoinitiator, includingunreacted photoinitiator and/or reacted photoinitiator fragments.

In some example embodiments, a silicone rubber 3D object may be formed.

1. Silicone Polyurethanes, Polyureas, or Poly(Urethane-Ureas).

In any of the preceding polyurethane examples, silicone orpoly(dimethylsiloxane) (PDMS) may be used as soft segment in theformation of these materials. For example, a (meth)acrylate-functionalABPU could be formed by first reacting an oligomeric PDMS diol ordiamine with two equivalents of diisocyanate to form a PDMS urethaneprepolymer. This material can be further reacted with TBAEMA or otherreactive blocking agents described herein to form a reactive blockedPDMS prepolymer which could be blended with chain extenders and reactivediluents as described in the examples above.

2. Silicone Interpenetrating Polymer Networks.

In some embodiments, the material may comprise, consists of or consistessentially of a UV-curable PDMS oligomer that is blended with atwo-part thermally curable PDMS oligomer system.

In example embodiments, 3D formed objects may have any of the aboveshapes or structures and may comprise or consist of or consistessentially of:

-   -   (i) A thermoset silicone or PDMS network cured by        platinum-catalyzed hydrosilation, tin-catalyzed condensation        chemistry, or peroxide initiated chemistry.    -   (ii) A UV-curable reactive diluent that is miscible with        silicone thermoset oligomers prior to curing. Example: an        acrylate-functional PDMS oligomer.    -   (iii) combinations thereof (optionally blended with reactive        diluents(s), for example as an interpenetrating polymer network,        a semi-interpenetrating polymer network, or as a sequential        interpenetrating polymer network), and/or    -   (iv) photoinitiator, including unreacted photoinitiator and/or        reacted photoinitiator fragments.

In an example embodiment, Phenylbis(2 4 6-trimethylbenzoyl)phosphineoxide (PPO) is dissolved in isobornyl acrylate (IBA) with a THINKY™mixer. Methacryloxypropyl terminated polydimethylsiloxane (DMS-R31;Gelest Inc.) is added to the solution, followed by addition of SylgardPart A and Part B (Corning PDMS precursors), and then further mixed witha THINKY™ mixer to produce a homogeneous solution. The solution isloaded into an apparatus as described above and a three-dimensionalintermediate is produced by ultraviolet curing as described above. Thethree-dimensional intermediate is then thermally cured at 100° C. for 12hours to produce the final silicone rubber product.

3. Epoxy Interpenetrating Networks.

In some example embodiments, an epoxy 3D object may be formed. Inexample embodiments, 3D formed objects may have any of the above shapesor structures and may comprise or consist of or consist essentially of:

-   -   (i) A thermoset epoxy network cured by the reaction of a        diepoxide with a diamine. Optionally, co-reactants may also be        included for example: co-reactants including polyfunctional        amines, acids (and acid anhydrides), phenols, alcohols, and        thiols;    -   (ii) A UV-curable reactive diluent that is miscible with the        epoxy thermoset precursors prior to curing;    -   (iii) combinations thereof (optionally blended with the reactive        diluent(s), for example as an interpenetrating polymer network,        a semi-interpenetrating polymer network, or as a sequential        interpenetrating polymer network), and/or    -   (iv) photoinitiator, including unreacted photoinitiator and/or        reacted photoinitiator fragments.

In an example embodiment: 10.018 g EpoxAcast 690 resin part A and 3.040g part B is mixed on a THINKY™ mixer. 3.484 g is then mixed with 3.013 gof RKP5-78-1, a 65/22/13 mix of SartomerCN9782/N-vinylpyrrolidone/diethyleneglycol diacrylate to give a clearblend which is cured under a Dymax ultraviolet lamp to produce anelastic 3D object.

In a second example embodiment, RKP11-10-1 containing 3.517 g of theabove epoxy and 3.508 g of RKP5-90-3 and 65/33/2/0.25 blend of SartomerCN2920/N-vinylcaprolactam/N-vinylpyrrolidone/PPO initiator is curedsimilarly to form a flexible 3D object.

In some example embodiments, the 3D formed object may include sol-gelcompositions, hydrophobic or hydrophilic compositions, phenolic resoles,cyanate esters, polyimides, conductive polymers, natural product basedIPNs, sequential IPNs and polyolefin as described above.

In example embodiments, 3D formed objects may have any of the shapes orstructures described above and may comprise or consist of or consistessentially of a plurality of different materials in different regionsof the 3D formed object with different tensile strength or other varyingproperties. In example embodiments, the differing materials may beselected from any of those describe above. In some example embodiments,the process of fabricating the product may be paused or interrupted oneor more times, to change the polymerizable liquid. In exampleembodiments, 3D formed objects may include multiple materials (whichmay, for example, be a thermoplastic or thermoset polyurethane,polyurea, or copolymer thereof or silicone rubber or epoxy orcombination of the foregoing) with different tensile strengths asdescribed further below. While a fault line or plane may be formed inthe intermediate by the interruption, if the subsequent polymerizableliquid is, in its second cure material, reactive with that of the first,then the two distinct segments of the intermediate will cross-react andcovalently couple to one another during the second cure (e.g., byheating or microwave irradiation). Thus, for example, any of thematerials described herein may be sequentially changed to form a producthaving multiple distinct segments with different tensile properties,while still being a unitary product with the different segmentscovalently coupled to one another.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) or silicone rubber or epoxy or combinationof the foregoing may comprise a majority of the 3D formed object byweight and may comprise more than 50%, 60%, 70%, 80% or 90% of the 3Dformed object by weight. In example embodiments, the polyurethane,polyurea, or copolymer thereof (e.g., poly(urethane-urea)) or siliconerubber or epoxy or combination of the foregoing may comprise or consistof or consist essentially of an interpenetrating network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network.

(i) Examples of Thermoplastic or Thermoset Polyurethane, Polyurea, orCopolymer Thereof (e.g., Poly(Urethane-Urea)).

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise a majority of the 3D formedobject by weight and may comprise more than 50%, 60%, 70%, 80% or 90% ofthe 3D formed object by weight.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of linear thermoplastic or thermoset polyurethane, polyurea,or copolymer thereof (e.g., poly(urethane-urea)). In exampleembodiments, the linear thermoplastic or cross-linked thermosetpolyurethane, polyurea, or copolymer thereof (e.g., poly(urethane-urea))may comprise a majority of the 3D formed object by weight and maycomprise more than 50%, 60%, 70%, 80% or 90% of the 3D formed object byweight.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of a polymer blend of (i) linear ethylenically unsaturatedblocking monomer copolymerized with reactive diluent and (ii) linearthermoplastic or cross-linked thermoset polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)). In example embodiments,the polymer blend may comprise a majority of the 3D formed object byweight and may comprise more than 50%, 60%, 70%, 80% or 90% of the 3Dformed object by weight. In example embodiments, the linearthermoplastic or cross-linked polyurethane, polyurea, or copolymerthereof (e.g., poly(urethane-urea)) may comprise or consist of orconsist essentially of linear poly(meth)acrylate.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of an interpenetrating network, a semi-interpenetratingpolymer network, or as a sequential interpenetrating polymer network ofethylenically unsaturated monomer and crosslinked or linearpolyurethane. In example embodiments, the network of ethylenicallyunsaturated monomer and crosslinked polyurethane may comprise a majorityof the 3D formed object by weight and may comprise more than 50%, 60%,70%, 80% or 90% of the 3D formed object by weight. In exampleembodiments, the linear thermoplastic or cross-linked thermosetpolyurethane, polyurea, or copolymer thereof (e.g., poly(urethane-urea))may comprise or consist of or consist essentially of crosslinkedpoly(meth)acrylate.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of an interpenetrating network, a semi-interpenetratingpolymer network, or as a sequential interpenetrating polymer network ofethylenically unsaturated monomer and linear thermoplastic orcross-linked thermoset polyurethane. In example embodiments, the networkof ethylenically unsaturated monomer and linear thermoplastic orcrosslinked thermoset polyurethane may comprise a majority of the 3Dformed object by weight and may comprise more than 50%/c, 60%, 70%, 80%or 90% of the 3D formed object by weight. In example embodiments, thelinear thermoplastic or cross-linked thermoset polyurethane, polyurea,or copolymer thereof (e.g., poly(urethane-urea)) may comprise or consistof or consist essentially of linear poly(meth)acrylate.

In some example embodiments, the 3D formed object may include sol-gelcompositions, hydrophobic or hydrophilic compositions, phenolic resoles,cyanate esters, polyimides, conductive polymers, natural product basedIPNs, sequential IPNs and polyolefins as described above.

(ii) Example Photoinitiator and Photoinitiator Fragments.

In example embodiments, the 3D formed object may include unreactedphotoinitiator remaining in the 3D formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount.

In example embodiments, because the systems, in part, consist ofmonomers and oligomers capable of being polymerized by exposure to UVlight, the end products will contain residual photoinitiator moleculesand photoiniator fragments.

In some embodiments, a photopolymerization will undergo thetransformation outlined below. In the first step, initiation, UV lightcleaves the initiator into active radical fragments. These activeradical fragments will go on to react with monomer group “M.” During thepropagation step, the active monomer will react with additional monomersthat attach to the growing polymer chain. Finally, termination can occureither by recombination or by disproportionation.

-   -   Initiation        -   Initiator+h_(v)→R^(⋅)        -   R^(⋅)+M→RM^(⋅)    -   Propagation        -   RM^(⋅)+M_(n)→RM_(n+1) ^(⋅)    -   Termination        -   combination        -   RM_(n) ^(⋅)+^(⋅)M_(m)R→RM_(n)M_(m)R        -   disproportionation        -   RM_(n) ^(⋅)+^(⋅)M_(m)R→RM_(n)+M_(m)R

In example embodiments, 3D formed objects generated by the processesoutlined herein may contain the following chemical products after theobject is created:

-   -   (1) Latent unreacted photoinitiator-photoinitiator is rarely        100% consumed during photopolymerization, therefore the product        will typically contain unreacted photoinitiators embedded        throughout the solid object:    -   (2) Photoinitiator by-products covalently attached to the        polymer network.

In example embodiments, photoinitiators may include the following:

(a) Benzoyl-Chromophore Based: These systems take the form

where “R” is any number of other atoms, including H, O, C, N, S. Theseinitiators cleave to form:

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(b) Morpholino and Amino Ketones. These systems take the form:

where “R” is any number of other atoms including H, O, C, N, S. Theseinitiators cleave to form

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(c) Benzoyl Phosphine Oxide. These systems take the form

where “R” is any number of other atoms including H, O, C, N, S. Theseinitiators cleave to form

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(d) Amines. Many photoinitiators may be used in combination with amines.Here the photoinitiators in the excited state serve to abstract ahydrogen atom from the amine, thus generating an active radical. Thisradical can go on to initiator polymerization and will therefore becomeincorporated into the formed polymer network. This process is outlinedbelow:

Either of these active species can go on to form an active polymer chainresulting in the structures below:

(e) Other systems. Other types of photoinitiators that may be used togenerate such materials and therefore will generate fragments which arecovalently attached to the formed polymer network include: triazines,ketones, peroxides, diketones, azides, azo derivatives, disulfidederivatives, disilane derivatives, thiol derivatives, diselenidederivatives, diphenylditelluride derivatives, digermane derivatives,distannane derivatives, carbo-germanium compounds, carbon-siliconderivatives, sulfur-carbon derivatives, sulfur-silicon derivatives,peresters, Barton's ester derivatives, hydroxamic and thiohydroxamicacids and esters, organoborates, organometallic compounds, titanocenes,chromium complexes, alumate complexes, carbon-sulfur or sulfur-sulfuriniferter compounds, oxyamines, aldehydes, acetals, silanes,phosphorous-containing compounds, borane complexes, thioxanthonederivatives, coumarins, anthraquinones, fluorenones, ferrocenium salts.

(f) Detection. Detection of the unique chemical fingerprint ofphotoinitiator fragments in a cured polymer object can be accomplishedby a number of spectroscopic techniques. Particular techniques usefulalone or in combination include: UV-Vis spectroscopy, fluorescencespectroscopy, infrared spectroscopy, nuclear magnetic resonancespectroscopy, mass spectrometry, atomic absorption spectroscopy, ramanspectroscopy, and X-Ray photoelectron spectroscopy.

D. Example Properties of 3D Objects.

The structural properties of the 3D formed object may be selectedtogether with the properties of the materials from which the 3D objectis formed to provide a wide range of properties for the 3D object. Dualcure materials and methods described above in the present applicationmay be used to form complex shapes with desired material properties toform a wide range of 3D objects.

In some embodiments, 3D formed objects may be rigid and have, forexample, a Young's modulus (MPa) in the range of about 800 to 3500 orany range subsumed therein, a Tensile Strength (MPa) in the range ofabout 30 to 100 or any range subsumed therein, and/or a percentelongation at break in the range of about 1 to 100 or any range subsumedtherein. Non-limiting examples of such rigid 3D formed objects mayinclude fasteners; electronic device housings; gears, propellers, andimpellers; wheels, mechanical device housings; tools and other rigid 3Dobjects.

In some embodiments, 3D formed objects may be semi-rigid and have, forexample, a Young's modulus (MPa) in the range of about 300-2500 or anyrange subsumed therein, a Tensile Strength (MPa) in the range of about20-70 or any range subsumed therein, and/or a percent elongation atbreak in the range of about 40 to 300 or 600 or any range subsumedtherein. Non-limiting examples of such rigid 3D formed objects mayinclude structural elements; hinges including living hinges; boat andwatercraft hulls and decks; wheels; bottles, jars and other containers;pipes, liquid tubes and connectors and other semi-rigid 3D objects.

In some embodiments, 3D formed objects may be elastomeric and have, forexample, a Young's modulus (MPa) in the range of about 0.5-40 or anyrange subsumed therein, a Tensile Strength (MPa) in the range of about0.5-30 or any range subsumed therein, and/or a percent elongation atbreak in the range of about 50-1000 or any range subsumed therein.Non-limiting examples of such rigid 3D formed objects may includefoot-wear soles, heels, innersoles and midsoles; bushings and gaskets;cushions; electronic device housings and other elastomeric 3D objects.

In Examples 18-61 are given materials for the formation of polyurethaneproducts having a variety of different tensile properties, ranging fromelastomeric, to semi-rigid, to flexible, as described above.

In some example embodiments, the process of fabricating the product maybe paused or interrupted one or more times, to change the polymerizableliquid. In example embodiments, 3D formed objects may include multiplematerials (which may, for example, be a thermoplastic or thermosetpolyurethane, polyurea, or copolymer thereof) with different tensilestrengths. While a fault line or plane may be formed in the intermediateby the interruption, if the subsequent polymerizable liquid is, in itssecond cure material, reactive with that of the first, then the twodistinct segments of the intermediate will cross-react and covalentlycouple to one another during the second cure (e.g., by heating ormicrowave irradiation). Thus, for example, any of the materialsdescribed herein may be sequentially changed to form a product havingmultiple distinct segments with different tensile properties, whilestill being a unitary product with the different segments covalentlycoupled to one another. In some embodiments, a 3D object may be formedwith a plurality of regions with different materials and properties. Forexample, a 3D formed object could have one or more regions formed from afirst material or first group of one or more materials having a TensileStrength (MPa) in the range of about 30-100 or any range subsumedtherein, and/or one or more regions formed from a second material orsecond group of one or more materials having a Tensile Strength (MPa) inthe range of about 20-70 or any range subsumed therein and/or one ormore regions formed from a third material or third group of one or morematerials having a Tensile Strength (MPa) in the range of about 0.5-30or any range subsumed therein or any combination of the foregoing. Forexample, the 3D object could have from 1-10 or more different regions(or any range subsumed therein) with varying tensile strength selectedfrom any of the materials and tensile strengths described above. Forexample, a hinge can be formed, with the hinge comprising a rigidsegment, coupled to a second elastic segment, coupled to a third rigidsegment, by sequentially changing polymerizable liquids (e.g., fromamong those described in Examples 19-60 above) during the formation ofthe three-dimensional intermediate. A shock absorber or vibrationdampener can be formed in like manner, with the second segment beingeither elastic or semi-rigid. A unitary rigid funnel and flexible hoseassembly can be formed in like manner.

E. Additional Examples of 3D Objects.

The above methods, structures, materials, compositions and propertiesmay be used to 3D print a virtually unlimited number of products.Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,catheters, bladder, breast implants, testicle implants, pectoralimplants, eye implants, contact lenses, dental aligners, microfluidics,seals, shrouds, and other applications requiring high biocompatibility,functional structures, microneedle arrays, fibers, rods, waveguides,micromechanical devices, microfluidic devices; fasteners; electronicdevice housings; gears, propellers, and impellers; wheels, mechanicaldevice housings; tools; structural elements; hinges including livinghinges; boat and watercraft hulls and decks; wheels; bottles, jars andother containers; pipes, liquid tubes and connectors; foot-ware soles,heels, innersoles and midsoles; bushings, o-rings and gaskets; shockabsorbers, funnel/hose assembly, cushions; electronic device housings;shin guards, athletic cups, knee pads, elbow pads, foam liners, paddingor inserts, helmets, helmet straps, head gear, shoe cleats, gloves,other wearable or athletic equipment, brushes, combs, rings, jewelry,buttons, snaps, fasteners, watch bands or watch housings, mobile phoneor tablet casings or housings, computer keyboards or keyboard buttons orcomponents, remote control buttons or components, auto dashboardcomponents, buttons, dials, auto body parts, paneling, other automotive,aircraft or boat parts, cookware, bakeware, kitchen utensils, steamersand any number of other 3D objects. The universe of useful 3D productsthat may be formed is greatly expanded by the ability to impart a widerange of shapes and properties, including elastomeric properties,through the use of multiple methods of hardening such as dual cure wherea shape can be locked-in using continuous liquid interface productionand subsequent thermal or other curing can be used to provideelastomeric or other desired properties. Any of the above describedstructures, materials and properties can be combined to form 3D objectsincluding the 3D formed products described above. These are examplesonly and any number of other 3D objects can be formed using the methodsand materials described herein.

XII. Washing of Intermediate Prior to Second Cure.

When desired, washing of the intermediate may be carried out by anysuitable technique, aided with any suitable apparatus, including but notlimited to those described in U.S. Pat. No. 5,248,456, the disclosure ofwhich is incorporated herein by reference.

Wash liquids that may be used to carry out the present inventioninclude, but are not limited to, water, organic solvents, andcombinations thereof (e.g., combined as co-solvents), optionallycontaining additional ingredients such as surfactants, chelants(ligands), enzymes, borax, dyes or colorants, fragrances, etc.,including combinations thereof. The wash liquid may be in any suitableform, such as a solution, emulsion, dispersion, etc.

Examples of organic solvents that may be used as a wash liquid, or as aconstituent of a wash liquid, include, but are not limited to, alcohol,ester, dibasic ester, ketone, acid, aromatic, hydrocarbon, ether,dipolar aprotic, halogenated, and base organic solvents, includingcombinations thereof. Solvents may be selected based, in part, on theirenvironmental and health impact (see, e.g., GSK Solvent Selection Guide2009).

Examples of alcohol organic solvents that may be used in the presentinvention include, but are not limited to, aliphatic and aromaticalcohols such as 2-ethyl hexanol, glycerol, cyclohexanol, ethyleneglycol, propylene glycol, di-propylene glycol, 1,4-butanediol, isoamylalcohol, 1,2-propanediol, 1,3-propanediol, benzyl alcohol, 2-pentanol,1-butanol, 2-butanol, methanol, ethanol, t-butanol, 2-propanol,1-propanol, 2-methoxyethanol, tetrahydrofuryl alcohol, benzyl alcohol,etc., including combinations thereof.

Examples of ester organic solvents that may be used to carry out thepresent invention include, but are not limited to, t-butyl acetate,n-octyl acetate, butyl acetate, ethylene carbonate, propylene carbonate,butylenes carbonate, glycerol carbonate, isopropyl acetate, ethyllactate, propyl acetate, dimethyl carbonate, methyl lactate, ethylacetate, ethyl propionate, methyl acetate, ethyl formate etc., includingcombinations thereof.

Examples of dibasic ester organic solvents include, but are not limitedto, dimethyl esters of succinic acid, glutaric acid, adipic acid, etc.,including combinations thereof.

Examples of organic ketone organic solvents that may be used to carryout the present invention include, but are not limited to,cyclohexanone, cyclopentanone, 2-pentanone, 3-pentanone, methylisobutylketone, acetone, methylethyl ketone, etc., including combinationsthereof.

Examples of acid organic solvents that may be used to carry out thepresent invention include, but are not limited to, propionic acid,acetic anhydride, acetic acid, etc., including combinations thereof.

Examples of aromatic organic solvents that may be used to carry out thepresent invention include, but are not limited to, mesitylene, cumene,p-xylene, toluene, benzene, etc., including combinations thereof.

Examples of hydrocarbon (i.e., aliphatic) organic solvents that may beused to carry out the present invention include, but are not limited to,cis-decalin, ISOPAR G, isooctane, methyl cyclohexane, cyclohexane,heptane, pentane, methylcyclopentane, 2-methylpentane, hexane, petroleumspirit, etc., including combinations thereof.

Examples of ether organic solvents that may be used to carry out thepresent invention include, but are not limited to, di(ethylene glycol),ethoxybenzene, tri(ethylene glycol), sulfolane, DEG monobutyl ether,anisole, diphenyl ether, dibutyl ether, t-amyl methyl ether,t-butylmethyl ether, cyclopentyl methyl ether, t-butyl ethyl ether,2-methyltetrahydrofuran, diethyl ether, bis(2-methoxyethyl) ether,dimethyl ether, 1,4-dioxane, tetrahydrofuran, 1,2-dimethoxyethane,diisopropyl ether, etc., including combinations thereof.

Examples of dipolar aprotic organic solvents that may be used to carryout the present invention include, but are not limited to,dimethylpropylene urea, dimethyl sulphoxide, formamide, dimethylformamide, N-methylformamide, N-methyl pyrrolidone, propanenitrile,dimethyl acetamide, acetonitrile, etc., including combinations thereof.

Examples of halogenated organic solvents that may be used to carry outthe present invention include, but are not limited to,1,2-dichlorobenzene, 1,2,4-trichlorobenzene, chlorobenzene,trichloroacetonitrile, chloroacetic acid, trichloroacetic acid,perfluorotoluene, perfluorocyclohexane, carbon tetrachloride,dichloromethane, perfluorohexane, fluorobenzene, chloroform,perfluorocyclic ether, trifluoracetic acid, trifluorotoluene,1,2-dichloroethane, 2,2,2-trifluoroethanol, etc., including combinationsthereof.

Examples of base organic solvents that may be used to carry out thepresent invention include, but are not limited to, N,N-dimethylaniline,triethylamine, pyridine, etc., including combinations thereof.

Examples of other organic solvents that may be used to carry out thepresent invention include, but are not limited to, nitromethane, carbondisulfide, etc., including combinations thereof.

Examples of surfactants include, but are not limited to, anionicsurfactants (e.g., sulfates, sulfonates, carboxylates, and phosphateesters), cationic surfactants, zwitterionic surfactants, nonionicsurfactants, etc., including combinations thereof. Common examplesinclude, but are not limited to, sodium stearate, linearalkylbenzenesulfonates, lignin sulfonates, fatty alcohol ethoxylates,alkylphenol ethoxylates, etc., including combinations thereof. Numerousexamples additional examples of suitable surfactants are known, some ofwhich are described in U.S. Pat. Nos. 9,198,847, 9,175,248, 9,121,000,9,120,997, 9,095,787, 9,068,152, 9,023,782, and 8,765,108.

Examples of chelants (chelating agents) include, but are not limited to,ethylenediamine tetraacetic acid, phosphates, nitrilotriacetic acid(NTA), citrates, silicates, and polymers of acrylic and maleic acid.

Examples of enzymes that may be included in the wash liquid include, butare not limited to, proteases, amylases, lipases, cellulases, etc.,including mixtures thereof. See, e.g., U.S. Pat. Nos. 7,183,248,6,063,206,

In some embodiments, the wash liquid can be an aqueous solution ofethoxylated alcohol, sodium citrate, tetrasodiumN,N-bis(carboxymethyl)-L-glutamate, sodium carbonate, citric acid, andisothiazolinone mixture. One particular example thereof is SIMPLE GREEN®all purpose cleaner (Sunshine Makers Inc., Huntington Beach, Calif.,USA) used per se or mixed with additional water.

In some embodiments, the wash liquid can be an aqueous solutioncomprised of 2-butoxyethanol, sodium metasilicate, and sodium hydroxide.One particular example thereof is PURPLE POWER™ degreaser/cleaner (AikenChemical Co., Greenville, S.C., USA), used per se or mixed withadditional water.

In some embodiments, the wash liquid can be ethyl lactate, alone or witha co-solvent. One particular example thereof is BIO-SOLV™ solventreplacement (Bio Brands LLC, Cinnaminson, N.J., USA), used per se ormixed with water.

In some embodiments, the wash liquid consists of a 50:50 (volume:volume)solution of water and isopropanol.

When the wash liquid includes ingredients that are not desired forcarrying into the further curing step, in some embodiments the initialwash with the wash liquid can be followed with a further rinsing stepwith a rinse liquid, such as water (e.g., distilled and/or deionizedwater), or a mixture of water and an alcohol such as isopropanol.

XII. Alternate Methods and Apparatus.

While the present invention is preferably carried out by continuousliquid interphase/interface polymerization, as described in detail aboveand in further detail below, in some embodiments alternate methods andapparatus for bottom-up or top-down three-dimension fabrication may beused, including layer-by-layer fabrication. Examples of such methods andapparatus include, but are not limited to, those described in U.S. Pat.No. 5,236,637 to Hull, U.S. Pat. Nos. 5,391,072 and 5,529,473 to Lawton,U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 to Shkolnik,U.S. Pat. No. 8,110,135 to El-Siblani, US Patent Application PublicationNos. 2013/0292862 to Joyce and 2013/0295212 to Chen et al., and PCTApplication Publication No. WO 2015/164234 to Robeson et al. Thedisclosures of these patents and applications are incorporated byreference herein in their entirety.

Elements and features that may be used in carrying out the presentinvention are explained in PCT Application Nos. PCT/US2014/015486(published as U.S. Pat. No. 9,211,678 on Dec. 15, 2015);PCT/US2014/015506 (also published as U.S. Pat. No. 9,205,601 on Dec. 8,2015), PCT/US2014/015497 (also published as US 2015/0097316, and U.S.Pat. No. 9,216,546 on Dec. 22, 2015), and in J. Tumbleston, D.Shirvanyants, N. Ermoshkin et al., Continuous liquid interfaceproduction of 3D Objects, Science 347, 1349-1352 (published online 16Mar. 2015).

Embodiments of the present invention are explained in greater detail inthe following non-limiting examples.

Example 1 High Aspect Ratio Adjustable Tension Build Plate Assembly

FIG. 6 is a top view and FIG. 7 is an exploded view of a 3 inch by 16inch “high aspect” rectangular build plate (or “window”) assembly of thepresent invention, where the film dimensions are 3.5 inches by 17inches. The greater size of the film itself as compared to the internaldiameter of vat ring and film base provides a peripheral orcircumferential flange portion in the film that is clamped between thevat ring and the film base, as shown in side-sectional view in FIG. 8.One or more registration holes (not shown) may be provided in thepolymer film in the peripheral or circumferential flange portion to aidin aligning the polymer film between the vat ring and film base, whichare fastened to one another with a plurality of screws (not shown)extending from one to the other (some or all passing through holes inthe peripheral edge of the polymer film) in a manner that securelyclamps the polymer film therebetween.

As shown in FIG. 7-FIG. 8 a tension ring is provided that abuts thepolymer film and stretches the film to tension, stabilize or rigidifythe film. The tension ring may be provided as a pre-set member, or maybe an adjustable member. Adjustment may be achieved by providing aspring plate facing the tension ring, with one or more compressibleelements such as polymer cushions or springs (e.g., flat springs, coilsprings, wave springs etc.) therebetween, and with adjustable fastenerssuch as screw fasteners or the like passing from the spring platethrough (or around) the tension ring to the film base.

Polymer films are preferably fluoropolymer films, such as an amorphousthermoplastic fluoropolymer, in a thickness of 0.01 or 0.05 millimetersto 0.1 or 1 millimeters, or more. In some embodiments we use BiogeneralTeflon AF 2400 polymer film, which is 0.0035 inches (0.09 millimeters)thick, and Random Technologies Teflon AF 2400 polymer film, which is0.004 inches (0.1 millimeters) thick.

Tension on the film is preferably adjusted with the tension ring toabout 10 to 100 pounds, depending on operating conditions such asfabrication speed.

The vat ring, film base, tension ring, and tension ring spring plate maybe fabricated of any suitable, preferably rigid, material, includingmetals (e.g., stainless steel, aluminum and aluminum alloys), carbonfiber, polymers, and composites thereof.

Registration posts and corresponding sockets may be provided in any ofthe vat ring, film base, tension ring and/or spring plate, as desired.

Example 2 Round Adjustable Tension Round Build Plate Assembly

FIG. 9 is a top view and FIG. 10 is an exploded view of a 2.88 inchdiameter round build plate of the invention, where the film dimensionmay be 4 inches in diameter. Construction is in like manner to thatgiven in Example 1 above, with a circumferential wave spring assemblyshown in place. Tension on the film is preferably adjusted to a liketension as given in Example 1 above (again depending on other operatingconditions such as fabrication speed).

FIG. 10 is an exploded view of the build plate of FIG. 9.

Example 3 Additional Embodiments of Adjustable Build Plates

FIG. 11 shows various alternate embodiments of the build plates of FIG.6-FIG. 10. Materials and tensions may be in like manner as describedabove.

Example 4 Example Embodiment of an Apparatus

FIG. 12 is a front perspective view, FIG. 13 is a side view and FIG. 14is a rear perspective view of an apparatus 100 according to an exemplaryembodiment of the invention. The apparatus 100 includes a frame 102 andan enclosure 104. Much of the enclosure 104 is removed or showntransparent in FIGS. 12-14.

The apparatus 100 includes several of the same or similar components andfeatures as the apparatus described above in reference to FIG. 2.Referring to FIG. 12, a build chamber 106 is provided on a base plate108 that is connected to the frame 102. The build chamber 106 is definedby a wall or vat ring 110 and a build plate or “window” such as one ofthe windows described above in reference to FIGS. 2 and 6-11.

Turning to FIG. 13, a carrier 112 is driven in a vertical directionalong a rail 114 by a motor 116. The motor may be any suitable type ofmotor, such as a servo motor. An exemplary suitable motor is the NXM45Amotor available from Oriental Motor of Tokyo, Japan.

A liquid reservoir 118 is in fluid communication with the build chamber106 to replenish the build chamber 106 with liquid resin. For example,tubing may run from the liquid reservoir 118 to the build chamber 106. Avalve 120 controls the flow of liquid resin from the liquid reservoir118 to the build chamber 106. An exemplary suitable valve is apinch-style aluminum solenoid valve for tubing available fromMcMaster-Carr of Atlanta, Ga.

The frame 102 includes rails 122 or other some other mounting feature onwhich a light engine assembly 130 (FIG. 15) is held or mounted. A lightsource 124 is coupled to the light engine assembly 130 using a lightguide entrance cable 126. The light source 124 may be any suitable lightsource such as a BlueWave® 200 system available from Dymax Corporationof Torrington, Conn.

Turning to FIG. 15, the light engine or light engine assembly 130includes condenser lens assembly 132 and a digital light processing(DLP) system including a digital micromirror device (DMD) 134 and anoptical or projection lens assembly 136 (which may include an objectivelens). A suitable DLP system is the DLP Discovery™ 4100 system availablefrom Texas Instruments, Inc. of Dallas, Tex. Light from the DLP systemis reflected off a mirror 138 and illuminates the build chamber 106.Specifically, an “image” 140 is projected at the build surface orwindow.

Referring to FIG. 14, an electronic component plate or breadboard 150 isconnected to the frame 102. A plurality of electrical or electroniccomponents are mounted on the breadboard 150. A controller or processor152 is operatively associated with various components such as the motor116, the valve 120, the light source 124 and the light engine assembly130 described above. A suitable controller is the Propeller Proto Boardavailable from Parallax, Inc. of Rocklin, Calif.

Other electrical or electronic components operatively associated withthe controller 152 include a power supply 154 and a motor driver 158 forcontrolling the motor 116. In some embodiments, an LED light sourcecontrolled by pulse width modulation (PWM) driver 156 is used instead ofa mercury lamp (e.g., the Dymax light source described above).

A suitable power supply is a 24 Volt, 2.5 A, 60 W, switching powersupply (e.g., part number PSI-60W-24 (HF60W-SL-24) available from MarlinP. Jones & Assoc, Inc. of Lake Park, Fla.). If an LED light source isused, a suitable LED driver is a 24 Volt, 1.4 A LED driver (e.g., partnumber 788-1041-ND available from Digi-Key of Thief River Falls, Minn.).A suitable motor driver is the NXD20-A motor driver available fromOriental Motor of Tokyo, Japan.

The apparatus of FIG. 12-FIG. 15 has been used to produce an “imagesize” of about 75 mm by 100 mm with light intensity of about 5 mW/cm².The apparatus of FIG. 12-FIG. 15 has been used to build objects atspeeds of about 100 to 500 mm/hr. The build speed is dependent on lightintensity and the geometry of the object.

Example 5 Another Example Embodiment of an Apparatus

FIG. 16 is a front perspective view of an apparatus 200 according toanother exemplary embodiment of the invention. The apparatus 200includes the same components and features of the apparatus 100 with thefollowing differences.

The apparatus 200 includes a frame 202 including rails 222 or othermounting feature at which two of the light engine assemblies 130 shownin FIG. 15 may be mounted in a side-by-side relationship. The lightengine assemblies 130 are configured to provide a pair of “tiled” imagesat the build station 206. The use of multiple light engines to providetiled images is described in more detail above.

The apparatus of FIG. 16 has been used to provide a tiled “image size”of about 150 mm by 200 mm with light intensity of about 1 mW/cm². Theapparatus of FIG. 16 has been used to build objects at speeds of about50 to 100 mm/hr. The build speed is dependent on light intensity and thegeometry of the object.

Example 6 Another Example Embodiment of an Apparatus

FIG. 18 is a front perspective view and FIG. 19 is a side view of anapparatus 300 according to another exemplary embodiment of theinvention. The apparatus 300 includes the same components and featuresof the apparatus 100 with the following differences.

The apparatus 300 includes a frame 302 including rails 322 or othermounting feature at which a light engine assembly 330 shown in FIG. 20may be mounted in a different orientation than the light assembly 130 ofthe apparatus 100. Referring to FIGS. 19 and 20, the light engineassembly 330 includes a condenser lens assembly 332 and a digital lightprocessing (DLP) system including a digital micromirror device (DMD) 334and an optical or projection lens assembly 336 (which may include anobjective lens). A suitable DLP system is the DLP Discovery™ 4100 systemavailable from Texas Instruments, Inc. of Dallas, Tex. Light from theDLP system illuminates the build chamber 306. Specifically, an “image”340 is projected at the build surface or window. In contrast to theapparatus 100, a reflective mirror is not used with the apparatus 300.

The apparatus of FIG. 18-FIG. 20 has been used to provide “image sizes”of about 10.5 mm by 14 mm and about 24 mm by 32 mm with light intensityof about 200 mW/cm² and 40 mW/cm² The apparatus of FIG. 18-FIG. 20 hasbeen used to build objects at speeds of about 10,000 and 4,000 mm/hr.The build speed is dependent on light intensity and the geometry of theobject.

Example 7 Control Program with Lua Scripting

Current printer technology requires low level control in order to ensurequality part fabrication. Physical parameters such as light intensity,exposure time and the motion of the carrier should all be optimized toensure the quality of a part. Utilizing a scripting interface to acontroller such as the Parallax PROPELLER™ microcontroller using theprogramming language “Lua” provides the user with control over allaspects of the printer on a low level. See generally R. Ierusalimschy,Programming in Lua (2013) (ISBN-10: 859037985X; ISBN-13:978-8590379850).

This Example illustrates the control of a method and apparatus of theinvention with an example program written utilizing Lua scripting.Program code corresponding to such instructions, or variations thereofthat will be apparent to those skilled in the art, is written inaccordance with known techniques based upon the particularmicrocontroller used.

Concepts. A part consists of slices of polymer which are formedcontinuously. The shape of each slice is defined by the frame that isbeing displayed by the light engine.

Frame. The frame represents the final output for a slice. The frame iswhat manifests as the physical geometry of the part. The data in theframe is what is projected by the printer to cure the polymer.

Slice. All the 2D geometry that will be outputted to a frame should becombined in a Slice. Slices can consist of procedural geometry, Slicesof a 3D model or any combination of the two. The slice generatingprocess allows the user to have direct control over the composition ofany frame.

Slice of a 3D Model. A slice is a special type of 2D geometry derivedfrom a 3D model of a part. It represents the geometry that intersects aplane that is parallel to the window. Parts are usually constructed bytaking 3D models and slicing them at very small intervals. Each slice isthen interpreted in succession by the printer and used to cure thepolymer at the proper height.

Procedural Geometry. Procedurally generated geometry can also be addedto a slice. This is accomplished by invoking shape generation functions,such as “addcircle”, “addrectangle”, and others. Each function allowsprojection of the corresponding shape onto the printing window. Aproduced part appears as a vertically extruded shape or combination ofshapes.

Coordinate spaces: Stage. The coordinate system that the stage uses isusually calibrated such that the origin is 1-20 microns above thewindow.

Coordinate spaces: Slice. Coordinate system of the projected slice issuch that origin is located at the center of the print window.

Quick Start.

The following is the most basic method of printing a part from a sliced3D model. Printing a sliced model consists of 4 main parts: Loading thedata, preparing the printer, printing, and shutdown.

Loading Data. In this section of the code the sliced model data isloaded into memory. The file path to the model is defined in theConstants section of the code. See the full code below for details.

--Loading Model

modelFilePath=“Chess King.svg”

numSlices=loadslices(modelFilePath)

Preparing the printer it is important to do two things before printing.You must first turn on the light engine with the relay function, and ifapplicable, the desired fluid height should be set.

--Prepare Printer

relay(true)--turn light on

showframe(−1)--ensure nothing is exposed durring setup

setlevels(.55, .6)--if available, printer set fluid pump to maintainabout 55% fill

Printing.

The first step of the printing process is to calibrate the system andset the stage to its starting position by calling gotostart. Next webegin a for loop in which we print each slice. The first line of the forloop uses the infoline command to display the current slice index in thesidebar. Next we determine the height at which the next slice should becured. That value is stored to nextHeight. Following this we move thestage to the height at which the next slice needs to be cured. To ensurea clean print it can sometimes be necessary to wait for oxygen todiffuse into the resin. Therefore we call sleep for a half second (theexact time for preExposureTime is defined in the constants section aswell). After this it's time to actually cure the resin so we callshowframe and pass it the index of the slice we want to print, which isstored in sliceIndex by the for loop. We sleep again after this forexposureTime seconds in order to let the resin cure. Before moving on tothe next frame, we call showframe(−1) in order to prevent the lightengine from curing any resin while the stage is moving to the nextheight.

--Execute Print

 gotostart( )--move stage to starting position  for sliceIndex=0,numSlices−1 do  infoline(5, string.format(″Current Slice: %d″,sliceIndex))  nextHeight = sliceheight(sliceIndex)--calculate the height that the stage should be at to  expose this frame  moveto(nextHeight,stageSpeed)--move to nextHeight  sleep(preExposureTime)--wait a givenamount of time for  oxygen to diffuse into resin ,  prepExposureTime ispredefined in the Constants section  showframe(sliceIndex)--show frameto expose  sleep(exposureTime)--wait while frame exposes, exposureTime is predefined in the  Constants section  showframe(−1)-- show nothingto ensure no exposure while stage  is moving to next position endShutdown.

The final step in the printing process is to shut down the printer. Callrelay(false) to turn the light engine off. If you are using fluidcontrol, call setlevels(0,0) to ensure the valve is shut off. Finally itis a good idea to move the stage up a bit after printing to allow foreasy removal of the part.

--Shutdown

relay(false)

setlevels(0,0)

--Lift stage to remove part

moveby(25, 16000)

Fully completed code implementing instructions based on the above is setforth below.

--Constants

exposureTime=1.5--in seconds

preExposureTime=0.5--in seconds

stageSpeed=300--in mm/hour

--Loading Model

modelFilePath=“Chess King.svg”

numSlices=loadslices(modelFilePath)

--calculating parameters

maxPrintHeight=sliceheight(numSlices−1)--find the highest point in theprint, this is the same as the height of the last slice. Slices are 0indexed, hence the −1.

infoline(1, “Current Print Info:”)

infoline(2, string.format(“Calculated Max Print Height: % dmm”,maxPrintHeight))

infoline(3, string.format(“Calculated Est. Time: % dmin”,(maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))

infoline(4, string.format(“Number of Slices: % d”, numSlices))

--Prepare Printer

relay(true)--turn light on

showframe(−1)--ensure nothing is exposed durring setup

setlevels(.55, .6)--if available, printer set fluid pump to maintainabout 55% fill

--Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do  infoline(5, string.format(″Current Slice: %d″,sliceIndex))  nextHeight = sliceheight(sliceIndex)--calculate the heightthat  the stage should  be at to expose this frame  moveto(nextHeight,stageSpeed)--move to nextHeight  sleep(preExposureTime)--wait a givenamount of time for oxygen  to diffuse into  resin , prepExposureTime ispredefined in the Constants section  showframe(sliceIndex)--show frameto expose  sleep(exposureTime)--wait while frame exposes, exposureTimeis  predefined in  the Constants section   showframe(−1)-- show nothingto ensure no exposure while stage is   moving to next  position end--Shutdownrelay(false)setlevels(0,0)--Lift stage to remove partmoveby(25, 16000)

Gotostart.

The main purpose of gotostart is to calibrate the stage. This functionresets the coordinate system to have the origin at the lowest point,where the limit switch is activated. Calling this command will move thestage down until the limit switch in the printer is activated; thisshould occur when the stage is at the absolute minimum height.

gotostart( ) moves stage to start at the maximum speed which varies fromprinter to printer.

gotostart( )--moving to origin at defauIt speed

gotostart(number speed) moves stage to start at speed given inmillimeters/hour.

gotostart(15000)--moving stage to origin at 15000 mm/hr

-speed: speed, in mm/hour, at which the stage will move to the startposition.

Moveto

moveto allows the user to direct the stage to a desired height at agiven speed. Safe upper and lower limits to speed and acceleration areensured internally. moveto(number targetHeight, number speed)

moveto(25/15000)--moving to 25 mm at 15,000 mm/hr

moveto(number targetHeight, number speed, number acceleration)

This version of the function allows an acceleration to be defined aswell as speed. The stage starts moving at initial speed and thenincreases by acceleration.

moveto(25, 20000, 1e7)--moving the stage to 25 mm at 20,000 mm/hr whileaccelerating at 1 million mm/hr{circumflex over ( )}2

moveto(number targetHeight, number speed, table controlPoints, functioncallback)

This function behaves similar to the basic version of the function. Itstarts at its initial speed and position and moves to the highest pointon the control point table, callback is called when the stage passeseach control point.

function myCallbackFunction(index)--defining the callback functionprint(″hello″) end

-   -   moveto(25, 20000, slicecontrolpoints( ),        myCallbackFunction)--moving the stage to 25 mm at 20,000 mm/hr        while calling myCallbackFunction at the control points generated        by slicecontrolpoints( )

-   moveto(number targetHeight, number speed, number acceleration, table    controlPoints, function callback) This function is the same as above    except the user can pass an acceleration. The stage accelerates from    its initial position continuously until it reaches the last control    point.

function myCallbackFunction(index)--defining the callback functionprint(″hello″) end

-   -   moveto(25, 20000, 0.5e7, slicecontrolpoints( ),        myCallbackFunction)--moving the stage to 25 mm at 20,000 mm/hr        while accelerating at 0.5 million mm/hr{circumflex over ( )}2        and also calling myCallbackFunction at the control points        generated by slicecontrolpoints( )    -   -targetHeight: height, in mm from the origin, that the stage        will move to.    -   -initialSpeed: initial speed, in mm/hour, that the stage will        start moving at.    -   -acceleration: rate, in mm/hour², that the speed of the stage        will increase from initial speed.    -   -controlPoints: a table of target heights in millimeters. After        the stage reaches a target height, it calls the function        callback.    -   -callback: pointer to a function that will be called when the        stage reaches a control point. The callback function should take        one argument which is the index of the control point the stage        has reached.        moveby

moveby allows the user to change the height of the stage by a desiredamount at a given speed. Safe upper and lower limits to speed andacceleration are ensured internally. moveby (number d Height, numberinitalSpeed)

1 moveby(−2, 15000)--moving down 2 mm at 15,000 mm/hr

moveby(number dHeight, number initialSpeed, number acceleration)

-   -   This version of the function allows an acceleration to be        defined as well as speed. The stage starts moving at initial        speed and then increases by acceleration until it reaches its        destination.    -   1 moveby(25, 15000, 1e7)--moving up 25 mm at 15,000 mm/hr while        accelerating 1e7 mm/hr{circumflex over ( )}2

moveby(number dHeight, number initialSpeed, table controlPoints,function callback)

-   -   This function usage allows the user to pass the function a table        of absolute height coordinates. After the stage reaches one of        these target heights, it calls the function ‘callback.’ Callback        should take one argument which is the index of the control point        it has reached.

function myCallbackFunction(index)--defining the callback function print(″hello″) end

-   -   moveby(25, 20000, slicecontrolpoints( ),        myCallbackFunction)--moving the stage up 25 mm at 20,000 mm/hr        while calling myCallbackFunction at the control points generated        by slicecontrolpoints( )

-   moveby(number dHeight, number initialSpeed, number acceleration,    table controlPoints, function callback) This function is the same as    above except the user can pass an acceleration. The stage    accelerates from its initial position continuously until it reaches    the last control point.

function myCallbackFunction(index)--defining the callback functionprint(″hello″) end

moveby(25, 20000, 1e7,slicecontrolpoints( ), myCallbackFunction)--movingthe stage up 25 mm at 20,000 mm/hr while calling myCallbackFunction atthe control points generated by slicecontrolpoints( ) and acceleratingat 1e7 mm/hr{circumflex over ( )}2

-   -   -dHeight: desired change in height, in millimeters, of the        stage.    -   -initialSpeed: initial speed, in mm/hour, at which the stage        moves.    -   -acceleration: rate, in mm/hour², that the speed of the stage        will increase from initial speed.    -   -controlPoints: a table of target heights in millimeters. After        the stage reaches a target height, it calls the function        callback.    -   -callback: pointer to a function that will be called when the        stage reaches a control point. The callback function should take        one argument which is the index of the control point the stage        has reached.        Light Engine Control        light    -   relay is used to turn the light engine on or off in the printer.        The light engine must be on in order to print. Make sure the        relay is set to off at the end of the script. relay(boolean        lightOn)

relay(true)--turning light on

-   -   -lightOn: false turns the light engine off, true turns the light        engine on.        Adding Procedural Geometry        Functions in this section exist to project shapes without using        a sliced part file. Every function in this section has an        optional number value called figureIndex. Each figure in a slice        has its own index. The figures reside one on top of another.        Figures are drawn so that the figure with the highest index is        ‘on top’ and will therefore not be occluded by anything below        it. By default indexes are assigned in the order that they are        created so the last figure created will be rendered on top. One        can, however, change the index by passing the desired index into        figureIndex.

Every function in this section requires a sliceIndex argument. Thisvalue is the index of the slice that the figure will be added to.

Note that generating this procedural geometry does not guarantee that itwill be visible or printable. One must use one of the functions such asfillmask or linemask outlined below.

addcircle

addcircle(number x, number y, number radius, number sliceIndex)addcircle draws a circle in the specified slice slice.

addCircle(0,0, 5, 0)--creating a circle at the origin of the first slicewith a radius of 5 mm

-   -   -x: is the horizontal distance, in millimeters, from the center        of the circle to the origin.    -   -y: is the vertical distance, in millimeters, from the center of        the circle to the origin.    -   -radius: is the radius of the circle measured in millimeters.    -   -sliceIndex: index of the slice to which the figure will be        added.    -   Returns: figure index of the figure.        addrectangle    -   addrectangle(number x, number y, number width, number height        number sliceIndex) addrectangle draws a rectangle in the        specified slice.        addrectangle(0,0, 5,5,0)--creating a 5 mm×5 mm square with its        top left corner at the origin.    -   -x: horizontal coordinate, in millimeters, of the top left        corner of the rectangle.    -   -y: vertical coordinate, in millimeters, of the top left corner        of the rectangle.    -   -width: width of the rectangle in millimeters.    -   -height: height of the rectangle in millimeters.    -   -sliceIndex: index of the slice to which the figure will be        added.    -   Returns: figure index of the figure.        addline    -   addline(number x0, number y0, number x1, number y1, number        sliceIndex) addline draws a line segment.        addLine(0,0, 20,20, 0)--creating a line from the origin to 20 mm        along the x and y axis on the first slice.    -   -x0: horizontal coordinate of the first point in the segment,        measured in millimeters.    -   -y0: vertical coordinate of the first point in the segment,        measured in millimeters.    -   -x1: horizontal coordinate of the second point in the segment,        measured in millimeters.    -   -y2: vertical coordinate of the second point in the segment,        measured in millimeters.    -   -sliceIndex: index of the slice to which the figure will be        added. Returns: figure index of the figure.        addtext

text(number x, number y, number scale, string text, number sliceIndex)addtext draws text on the specified slice starting at position ‘x, y’with letters of size ‘scale’.

addtext(0,0, 20, “Hello world”, 0)--writing Hello World at the origin ofthe first slice

-   -   -x: horizontal coordinate, measured in millimeters, of the top        left corner of the bounding box around the text.    -   -y: vertical coordinate, measured in millimeters, of the top        left corner of the bounding box around the text.    -   -scale: letter size in millimeters, interpretation may vary        depending on the underlying operating system (Windows, OSX,        Linux, etc).    -   -text: the actual text that will be drawn on the slice.    -   -sliceIndex: index of the slice to which the figure will be        added. Returns: figure index of the figure.        Fill and Line Control        fillmask    -   fillmask(number color, number sliceIndex, number figureIndex)        fillmask is used to control how the procedural geometry is        drawn, fillmask tells the figure in question to fill the        entirety of its interior with color.        -   -color, can be any number on the range 0 to 255. Where 0 is            black and 255 is white, any value in between is a shade of            grey interpolated linearly between black and white based on            the color value. Any value less than 0 will produce a            transparent color.        -   myCircle=addCircle(0,0,5,0)--creating the circle to fill        -   fillmask(255,0, myCircle)--Creating a white filled circle        -   -sliceIndex:the index of the slice that should be modified.        -   -figureIndex:the is used to determine which figure on the            slice should be filled.        -   Each figure has its own unique index. If no figureIndex is            passed, the fill applies to all figures in the slice.            linemask    -   linemask(number color, number sliceIndex, number figureIndex)        linemask is used to control how the procedural geometry is        drawn, linemask tells a figure to draw its outline in a specific        color. The width of the outline is defined by the function        linewidth.        -   myCircle=addCircle(0,0,20,0)--creating the circle to fill        -   linemask(255, 0, myCircle)--settingthe outline of the circle            to be white        -   fillmask(150,0, myCircle)--setting the fill of the circle to            be grey        -   -color: can be any number on the range 0 to 255. Where 0 is            black and 255 is white, any value in between is a shade of            grey interpolated linearly between black and white based on            the color value. Any value less than 0 will produce a            transparent color.        -   -sliceIndex: the index of the slice that should be modified.        -   -figureIndex: is used to determine which figure on the slice            should be filled.        -   Each figure has its own unique index. If no figureIndex is            passed, the fill applies to all figures in the slice.            linewidth    -   linewidth(nuniher widthy number sliceIndex, number figureIndex)        linewidth is used to set the width of the line that linemask        will use to outline the figure.    -   linewidth(2,0)--setting the line width for every figure on the        first slice to 2 mm        -   -sliceIndex: the index of the slice that should be modified.        -   -figureIndex: is used to determine which figure on the slice            should have its outline changed. Each figure has its own            unique index, see section 2.3 (Pg. 10) for more details. If            no figureIndex is passed, the fill applies to all figures in            the slice.            loadmask    -   loadmask(string filepath) loadmask allows for advanced fill        control. It enables the user to load a texture from a bitmap        file and use it to fill the entirety of a figure with the        texture.        -   texture=loadmask(“voronoi_noise.png”)--loading texture.            voronoi_noise.png is in the same directory as the script.        -   myCircle=addCircle(0,0,20,0)--creating the circle to fill        -   fillmask(texture, 0, myCircle)--filling the circle with            voronoi noise        -   filepath: file path to image file        -   Returns: a special data type which can be passed into a            fillmask or linemask function as the color argument.            Frames            showframe    -   showframe(number sliceIndex) showframe is essential to the        printing process. This function sends the data from a slice to        the printer. Call showframes on a frame that doesn't exist to        render a black frame e.g., showframe(−1).

showframe(2)--showing the 3rd slice

-   -   -sliceIndex: the index of the slice to send to the printer.        framegradient    -   framegradient(number slope) framegradient is designed to        compensate for differences in light intensity.        calcframc

calcframe( )

-   -   calcframe is designed to analyze the construction of a slice        calculates the last frame shown.    -   showframe(0)    -   calcframe( )    -   Returns: the maximum possible distance between any point in the        figure and the edge.

2.5.4 loadframe

loadframe(string filepath)

-   -   loadframe is used to load a single slice from a supported bitmap        file.    -   loadframe(“slice.png”)--slice.png is in the same directory as        the script        -   -filepath: file path to slice image.            Slices

addslice

-   -   addslice(number sliceHeight) addslice creates a new slice at a        given height at the end of the slice stack.    -   addslice(.05)--adding a slice at .05 mm

addslice(number sliceHeight, number sliceIndex)

-   -   addslice(.05, 2)--adding a slice at .05 mm and at index 2. this        pushes all layers 2 and higher up an index.        -   addslice creates a new slice at a given height and slice            index.        -   -sliceHeight: height, in millimeters, of the slice.        -   -sliceIndex: index at which the slice should be added.            Returns: slice index.

loadslices

-   -   loadslices(string filepath) loadslices is used to load all the        slices from a 2D slice file.

loadslices(“Chess King.svg”)--loading all the slices from the ChessKing.svg file

-   -   -filepath: file path to the sliced model. Acceptable formats are        .cli and .svg. Returns: number of slices.        sliceheight    -   sliceheight(number sliceIndex) sliceheight is used to find the        height of a slice in mm off the base.        -   addslice(.05,0)--setting the first slice to .05 mm        -   sliceheight(0)--checking the height of slice 0, in this            example it should return .05        -   -sliceIndex: index of the slice to check. Returns: slice            height in mm.2.6.4 slicecontrolpoints    -   slicecontrolpoints( ) slicecontrolpoints is a helper function        which creates a control point for each slice of a model. These        control points can be passed to the moveto or moveby function to        set it to callback when the stage reaches the height of each        slice. Make sure loadslices has been called prior to calling        this function.        loadslices(“Chess King.svg”)        controlPoints=slicecontrolpoints( )

Returns: Lua table of control points.

Timing

Sleep

-   -   sleep(number seconds) sleep allows the user to pause the        execution of the program for a set number of seconds.        sleep(.5)--sleeping for a half second    -   -seconds: number of seconds to pause script execution.        Clock    -   clock( ) clock returns the current time in seconds. It is        accurate at least up to the millisecond and should therefore be        used instead of Lua's built in clock functionality, clock should        be used as a means to measure differences in time as the start        time for the second count varies from system to system.        -   t1=clock( )        -   loadslices(“Chess King.svg”)        -   deltaTime=clock( )-t1        -   Returns: system time in seconds.            Fluid Control

This set of functions can be used with printer models that support fluidcontrol. Before the script finishes executing, setlevels(0,0) should becalled to ensure that the pump stops pumping fluid into the vat.

getcurrentlevel

-   -   getcurrentlevel( ) getcurrentlevel returns the percentage of the        vat that is full.

print(string.format(“Vat is % d percent full.”, getcurrentlevel( )*100))

-   -   Returns: a floating point number on the range 0 to 1 that        represents the percentage of the vat that is full.        setlevels    -   setlevels(number min, number max) setlevels allows the user to        define how much fluid should be in the vat. The fluid height        will be automatically regulated by a pump. The difference        between min and max should be greater than 0.05 to ensure that        the valve is not constantly opening and closing.

setlevels(.7,.75)--keeping vat about 75 percent full

-min: the minim percentage of the vat that should be full. Entered as afloating point number from 0 to 1.

-   -   -max: the max percentage of the vat that should be full. Entered        as a floating point number from 0 to 1.        User Feedback

infoline

-   -   infoline(int lineIndex, string text) infoline allows the user to        display up to 5 lines of text in a constant position on the        sidebar of the Programmable Printer Platform. This function is        often used to allow the user to monitor several changing        variables at once.

infoline(1, string.format(“Vat is % d percent full.”, getcurrentlevel()*100))

-   -   -lineIndex: the index of the line. Indexes should be in the        range 1 to 5, 1 being the upper most line, -text: text to be        displayed at line index.        Global Configuration Table.

Before a print script is executed, all global variables are loaded intoa configuration table called cfg. Most of the data in this table hasalready been read by the Programmable Printer Platform by the time theusers script executes, therefore, changing them will have no effect.However, writing to the xscale, yscale, zscale, xorig and yorig fieldsof the cfg, will effect all the loadslices and addlayer calls that aremade afterwards. If the users script is designed to be run at a specificscale and/or position, it is good practice to override the cfg with thecorrect settings to ensure the scale and position can't be accidentallychanged by the Programmable Printer Platform.

cfg.xscale=3--overriding global settings to set scale on the x axis to 3

cfg.yscale=2--overriding global settings to set scale on the y axis to 2

cfg.zscale=1--overriding global settings to set scale on the z axis to 1

cfg.xorig=−2.0--overriding global settings to set the origin on the xaxis 2 mm left

cfg.yorig=0.25--overriding global settings to set the origin on the yaxis .25 mm in the positive direction

Fields in cfg:

-serial port: name of serial port (changing this variable wont effectcode)

-xscale: x scale-yscale: y scale

-zscale: z scale

-xorig: x origin-yorig: y origin

-hw xscale: pixel resolution in x direction (changing this variablewon't effect code)

-hw yscale: pixel resolution in y direction (changing this variablewon't effect code)

Useful Lua Standard Libraries.

The math standard library contains several different functions that areuseful in calculating geometry. The string object is most useful inprinting for manipulating info strings. For details contact LabLua atDepartamento de Informática, PUC-Rio, Rua Marquês de São Vicente, 225;22451-900 Rio de Janeiro, RJ, Brazil.

Example 8 Lua Script Program for Continuous Print

This example shows a Lua script program corresponding to Example 7 abovefor continuous three dimension printing.

--Constants

sliceDepth=.05--in millimeters

exposureTime=.225--in seconds

-Loading Model

modelFilePath=“Chess King.svg”

numSlices=loadslices(modelFilePath)

controlPoints=slicecontrolpoints( )--Generate Control Points

-calculating parameters

exposureTime=exposureTime/(60*60)--converted to hours

stageSpeed=sliceDepth/exposureTime--required distance/required time

maxPrintHeight=sliceheight(numSlices−1)--find the highest point in theprint, this is the same as the height of the last slice. Slices are 0indexed, hence the −1.

infoline(1, “Current Print Info:”)

infoline(2, string.format(“Calulated Stage Speed: % dmm/hr\n”,stageSpeed))

infoline(3, string.format(“Calculated Max Print Height: % dmm”,maxPrintHeight))

infoline(4, string.format(“Calculated Est. Time: % dmin”,

(maxPrintHeight/stageSpeed)*60))

--Create Callback Function for use with moveto

function movetoCallback(controlPointIndex)  showframe(controlPointIndex)end

--Prepare Printer

relay(true)--turn light on

setlevels(.55, .6)--if available, printer set fluid pump to maintainabout 50% fill

--Execute Print

gotostart( )--move stage to starting position

moveto(maxPrintHeight, stageSpeed, controlPoints, movetoCallback)

--Shutdown

relay(false)

setlevels(0,0)

--Lift stage to remove part

moveby(25, 160000)

Example 9 Lua Script Program for Cylinder and Buckle

This example shows a Lua script program for two fitted parts that useprocedural geometry.

Cylinder:

--Constants

exposureTime=1.5--in seconds

preExposureTime=1--in seconds

stageSpeed=300--in mm/hour

sliceDepth=.05

numSlices=700

--Generating Model

radius = 11 thickness = 4 smallCircleRad = 1.4 for sliceIndex =0,numSlices−1 do  addlayer(sliceDepth*(sliceIndex+1), sliceIndex)--the depth of a slice*its index =   height of slice  largeCircle =addcircle(0,0,radius, sliceIndex)  linewidth(thickness, sliceIndex,largeCircle)  linemask(255, sliceIndex, largeCircle)  for i=0,2*math.pi,2*math.pi/8 do    addcircle(math.cos(i)*radius, math.sin(i)*radius,   smallCircleRad, sliceIndex)  end  fillmask(0,sliceIndex) end

--calculating parameters

-   maxPrintHeight=sliceheight(numSlices−1)--find the highest point in    the print, this is the same as the height of the last slice. Slices    are 0 indexed, hence the −1.-   infoline(1, “Current Print Info:”)-   infoline(2, string.format(“Calculated Max Print Height: % dmm”,    maxPrintHeight))-   infoline(3, string.format(“Calculated Est. Time: % dmin”,    (maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))-   infoline(4, string.format(“Number of Slices: % d”, numSlices))

--Prepare Printer

relay(true)--turn light on

showframe(−1)--ensure nothing is exposed durring setup

setlevels(.55, .6)--if available, printer set fluid pump to maintainabout 55% fill

--Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do  infoline(5, string.format(″Current Slice: %d″,sliceIndex))  nextHeight = sliceheight(sliceIndex)--calculate the heightthat the stage  should be at to expose this frame  moveto(nextHeight,stageSpeed)--move to nextHeight  sleep(preExposureTime)--wait a givenamount of time for  oxygen to diffuse into  resin , prepExposureTime ispredefined in the Constants section  showframe(sliceIndex)--show frameto expose  sleep(1.5)--wait while frame exposes, exposureTime ispredefined  in the Constants  section  showframe(−1)-- show nothing toensure no exposure while stage  is moving to next  position end

--Shutdown

relay(false)

setlevels(0,0)

--Lift stage to remove part

moveby(25, 160000)

Buckle:

--Constants

exposureTime=1.5--in seconds

preExposureTime=0.5--in seconds

stageSpeed-300 --in mm/hour

sliceDepth=.05

numSlices=900

--Generating Model

 baseRadius = 11  thickness = 3  innerCircieRad = 7.5  for sliceIndex =0,numSlices−1 do   addlayer(sliceDepth*(sliceIndex+1))--the depth of aslice*its   index = height of  slice      if(sliceIndex < 100) then--base       addcircle(0,0, baseRadius, sliceIndex)       fillmask(255,sliceIndex)      else -- inner circle       innerCircle = addcircle(0,0,innerCircleRad, sliceIndex)       linewidth(thickness, sliceIndex,innerCircle)       linemask(255, sliceIndex, innerCircle)    for i =0,4*2*math.pi/8, 2*math.pi/8 do         x =math.cos(i)*(innerCircleRad+thickness)         y =math.sin(i)*(innerCircleRad+thickness)         cutline = addline(x,y,−x,−y, sliceIndex)         linewidth(3, sliceIndex, cutLine)        linemask(0, sliceIndex, cutLine)     end       if (sliceIndex >800) then --tips          r0 = innerCircleRad +2          if(sliceIndex< 850) then   r0 = innerCircleRad + (sliceIndex−800)*(2/50)        end      for i = 0,4*2*math.pi/8, 2*math.pi/8 do   ang = i +(2*math.pi/8)/2   x = math.cos(ang)*(r0)   y = math.sin(ang)*(r0)  nubLine = addline(x,y, −x,−y, sliceIndex)   linewidth(2, sliceIndex,nubLine)   linemask(255, sliceIndex, nubLine)        end       fillmask(0,sliceIndex, addcircle(0,0, innerCircleRad-       (thickness/2),      sliceIndex))   end end showframe(sliceIndex)sleep(.02) end--calculating parametersmaxPrintHeight=sliceheight(numSlices−1)--find the highest point in theprint, this is the same as the height of the last slice. Slices are 0indexed, hence the −1.infoline(1, “Current Print Info:”)infoline(2, string.format(“Calculated Max Print Height: % dmm”,maxPrintHeight))infoline(3, string.format(“Calculated Est. Time: % dmin”,(maxPrintHeight/stageSpeed)*60+(preExposureTime+exposureTime)*numSlices/60))infoline(4, string.format(“Number of Slices: % d”, numSlices))--Prepare Printerrelay(true)--turn light onshowframe(−1)--ensure nothing is exposed during setupsetlevels(.55, .6)--if available, printer set fluid pump to maintainabout 55% fill--Execute Print

gotostart( )--move stage to starting position for sliceIndex=0,numSlices−1 do  infoline(5, string.format(″Current Slice: %d″,sliceIndex))  nextHeight = sliceheight(sliceIndex)--calculate the heightthat  the stage should  be at to expose this frame  moveto(nextHeight,stageSpeed)--move to nextHeight  sleep(preExposureTime)--wait a givenamount of time for oxygen  to diffuse into resin,  prepExposureTime ispredefined in the Constants section  showframe(sliceIndex)--show frameto expose  sleep(1.5)--wait while frame exposes, exposureTime ispredefined  in the Constants section  showframe(−1)-- show nothing toensure no exposure while stage  is moving to next position end--Shutdownrelay(false)setlevels(0,0)--Lift stage to remove partmoveby(25, 160000)

Example 10 Continuous Fabrication with Intermittent Irradiation andAdvancing

A process of the present invention is illustrated in FIG. 21, where thevertical axis illustrates the movement of the carrier away from thebuild surface. In this embodiment, the vertical movement or advancingstep (which can be achieved by driving either the carrier or the buildsurface, preferably the carrier), is continuous and unidirectional, andthe irradiating step is carried out continuously. Polymerization of thearticle being fabricated occurs from a gradient of polymerization, andhence creation of “layer by layer” fault lines within the article isminimized.

An alternate embodiment of the present invention is illustrated in FIG.22. In this embodiment, the advancing step is carried out in astep-by-step manner, with pauses introduced between active advancing ofthe carrier and build surface away from one another. In addition, theirradiating step is carried out intermittently, in this case during thepauses in the advancing step. We find that, as long as the inhibitor ofpolymerization is supplied to the dead zone in an amount sufficient tomaintain the dead zone and the adjacent gradient of polymerizationduring the pauses in irradiation and/or advancing, the gradient ofpolymerization is maintained, and the formation of layers within thearticle of manufacture is minimized or avoided. Stated differently, thepolymerization is continuous, even though the irradiating and advancingsteps are not. Sufficient inhibitor can be supplied by any of a varietyof techniques, including but not limited to: utilizing a transparentmember that is sufficiently permeable to the inhibitor, enriching theinhibitor (e.g., feeding the inhibitor from an inhibitor-enriched and/orpressurized atmosphere), etc. In general, the more rapid the fabricationof the three-dimensional object (that is, the more rapid the cumulativerate of advancing), the more inhibitor will be required to maintain thedead zone and the adjacent gradient of polymerization.

Example 11 Continuous Fabrication with Reciprocation During Advancing toEnhance Filling of Build Region with Polymerizable Liquid

A still further embodiment of the present invention is illustrated inFIG. 23. As in Example 10 above, this embodiment, the advancing step iscarried out in a step-by-step manner, with pauses introduced betweenactive advancing of the carrier and build surface away from one another.Also as in Example 10 above, the irradiating step is carried outintermittently, again during the pauses in the advancing step. In thisexample, however, the ability to maintain the dead zone and gradient ofpolymerization during the pauses in advancing and irradiating is takenadvantage of by introducing a vertical reciprocation during the pausesin irradiation.

We find that vertical reciprocation (driving the carrier and buildsurface away from and then back towards one another), particularlyduring pauses in irradiation, can serve to enhance the filling of thebuild region with the polymerizable liquid, apparently by pullingpolymerizable liquid into the build region. This is advantageous whenlarger areas are irradiated or larger parts are fabricated, and fillingthe central portion of the build region may be rate-limiting to anotherwise rapid fabrication.

Reciprocation in the vertical or Z axis can be carried out at anysuitable speed in both directions (and the speed need not be the same inboth directions), although it is preferred that the speed whenreciprocating away is insufficient to cause the formation of gas bubblesin the build region.

While a single cycle of reciprocation is shown during each pause inirradiation in FIG. 23, it will be appreciated that multiple cycles(which may be the same as or different from one another) may beintroduced during each pause.

As in Example 10 above, as long as the inhibitor of polymerization issupplied to the dead zone in an amount sufficient to maintain the deadzone and the adjacent gradient of polymerization during thereciprocation, the gradient of polymerization is maintained, theformation of layers within the article of manufacture is minimized oravoided, and the polymerization/fabrication remains continuous, eventhough the irradiating and advancing steps are not.

Example 12 Acceleration During Reciprocation Upstroke and DecelerationDuring Reciprocation Downstroke to Enhance Part Quality

We observe that there is a limiting speed of upstroke, and correspondingdownstroke, which if exceeded causes a deterioration of quality of thepart or object being fabricated (possibly due to degradation of softregions within the gradient of polymerization caused by lateral shearforces a resin flow). To reduce these shear forces and/or enhance thequality of the part being fabricated, we introduce variable rates withinthe upstroke and downstroke, with gradual acceleration occurring duringthe upstroke and gradual deceleration occurring during the downstroke,as schematically illustrated in FIG. 24.

Example 13 Dual Cure with PEGDA+EGDA+Polyurethane (HMDI Based)

5 g of the following mixture was mixed for 3 minutes in a high-shearmixer.

-   -   1 g of poly(ethylene glycol) diacrylate (Mn=700 g/mol)        containing 12 wt % of diphenyl(2 4 6-trimethylbenzoyl)phosphine        oxide (DPO).    -   1 g of diethyleneglycol diacrylate containing 12 wt % DPO    -   1 g of “Part A” polyurethane resin (Methylene        bis(4-Cyclohexylisocyanate) based: “ClearFlex 50” sold by        Smooth-On® inc.    -   2 g of “Part B” polyurethane resin (polyol mixture): “ClearFlex        50” sold by Smooth-On® inc.    -   0.005 g of amorphous carbon black powder

After mixing, the resin was 3D formed using an apparatus as describedherein. A “honeycomb” object was formed at a speed of 160 mm/hr using alight intensity setting of 1.2 mV (when measured using a volt meterequipped with a optical sensor). Total printing time was approximately10 minutes.

After printing, the part was removed from the print stage, rinsed withhexanes, and placed into an oven set at 110° C. for 12 hours.

After heating, the part maintained its original shape generated duringthe initial printing, and it had transformed into a tough, durable,elastomer having an elongation at break around 200%

Example 14 Dual Cure with EGDA+Polyurethane (TDI Based)

5 g of the following mixture was mixed for 3 minutes in a high-shearmixer.

-   -   1 g of diethyleneglycol diacrylate containing 12 wt % DPO    -   2 g of “Part A” polyurethane resin (toluene diisocyanate) based:        “VytaFlex 30” sold by Smooth-On® inc.    -   2 g of “Part B” polyurethane resin (polyol mixture): “Vytaflex        30” sold by Smooth-On® inc.

After mixing, the resin was 3D formed using an apparatus as describedherein. The cylindrical object was formed at a speed of 50 mm/hr using alight intensity setting of 1.2 mV (when measured using a volt meterequipped with an optical sensor). Total printing time was approximately15 minutes.

After printing, the part was removed from the print stage, rinsed withhexanes, and placed into an oven set at 110° C. for 12 hours.

After heating, the part maintained its original shape generated duringthe initial printing, and it had transformed into a tough, durable,elastomer having an elongation at break around 400%.

Example 15 Synthesis of a Reactive Blocked Polyurethane Prepolymer forDual Cure

Add 200 g of melted anhydrous 2000 Da, polytetramethylene oxide (PTMO2k)into a 500 mL 3-neck flask charged with an overhead stirrer, nitrogenpurge and a thermometer. Then 44.46 g IPDI is added to the flask andstirred to homogeneous solution with the PTMO for 10 min, followed byaddition of 140 uL Tin(II) catalyst stannous octoate. Raise thetemperature to 70° C., and keep reaction for 3 h. After 3 h, graduallylower the temperature to 40° C., and gradually add 37.5 g TBAEMA usingan additional funnel within 20 min. Then set the temperature to 50° C.and add 100 ppm hydroquinone. Keep the reaction going on for 14 h. Pourout the final liquid as the product.

Example 16 Synthesis of a Second Reactive Blocked PolyurethanePrepolymer for Dual Cure

Add 150 g dried 1000 Da, polytetramethylene oxide (PTMO1k) into a 500 mL3-neck flask charged with an overhead stirrer, nitrogen purge and athermometer. Then 50.5 g HDI is added to the flask and stirred tohomogeneous solution with the PTMO for 10 min, followed by addition of100 uL Tin(II) catalyst stannous octoate. Raise the temperature to 70°C., and keep reaction for 3 h. After 3 h, gradually lower thetemperature to 40° C., and gradually add 56 g TBAEMA using an additionalfunnel within 20 min. Then set the temperature to 50° C. and add 100 ppmhydroquinone. Keep the reaction going on for 14 h. Pour out the finalliquid as the product.

In the above examples, the PTMO can be replaced by polypropylene glycol(PPG, such as 1000 Da PPG (PPG1k)) or other polyesters or polybuadienediols. IPDI or HDI can be replaced by other diisocyanates. The molarstoichiometry of the polyol:diisocyanate:TBAEMA is preferably 1:2:2.Preferably use 0.1-0.3 wt % stannous octoate to the weight of thepolyol.

Example 17 Printing and Thermal Curing with a Reactive BlockedPolyurethane Prepolymers

ABPU resins can be formed (optionally but preferably by continuousliquid interphase/interface printing) at up to 100 mm/hr using theformulations in Table 1 to generate elastomers with low hysteresis afterthermally cured at 100° C. for 2 to 6 hours, depending on thediisocyanates used in ABPU and the chain extender(s).

TABLE 1 Parts by weight ABPU 320 Reactive Diluent 40-80 Ethylene glycol 8-20 H12MDA  8-20 PPO 1-4

Dog-bone-shaped specimens were formed by continuous liquid interfaceprinting with different ABPUs (varying the diisocyanate and polyol usedfor the synthesis) and reactive diluents. Table 2 shows the mechanicalproperties of some of the thermally cured dog-bone samples at roomtemperature.

TABLE 2 Tensile stress ABPU Reactive at maximum load % elongationDiisocyanate Polyol diluent (MPa) at break IPDI PTMO2k Methyl 25 650methacrylate IPDI PPG1k Cyclohexane 7.5 368 methacrylate MDI PTMO2kTBAEMA 13.4 745 HDI PTMO1k TBAEMA 13 490 HMDI PTMO1k TBAEMA 13.6 334

Examples 18-61 Additional Polyurethane Dual Cure Materials. Testing andTensile Properties

The following abbreviations are used in the Examples below: “DEGMA”means di(ethylene glycol) methyl ether methacrylate; “IBMA” meansisoboronyl methacrylate; “PACM” means 4,4′-Diaminodicyclohexyl methane;“BDO” means 1,4-butanediol; “PPO” meansPhenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; “MDEA” means4,4′-methylene-bis-(2,6-diethylaniline); “2-EHMA” means 2-ethylhexylmethacrylate; and “PEGDMA” means poly(ethylene glycol) dimethacrylate(MW=700 Da).

Example 18 Testing of Tensile Properties

In the examples above and below, tensile properties were tested inaccordance with ASTM standard D638-10, Standard Test Methods for TensileProperties of Plastics (ASTM International, 100 Barr Harbor Drive, POBox C700, West Conshohocken, Pa., 19428-2959 USA).

Briefly, tensile specimens (sometimes referred to as “dog-bone samples”in reference to their shape), were loaded onto an Instron 5964 testingapparatus with Instron BLUEHILL3 measurement software (Instron, 825University Ave, Norwood, Mass., 02062-2643, USA). The samples areoriented vertically and parallel to the direction of testing. Cast andflood cured samples were fully cured using a DNMAX 5000 EC-Seriesenclosed UV flood lamp (225 mW/cm²) for from thirty to ninety seconds ofexposure. Table 3 below summarizes the types of tensile specimenstested, general material property (rigid or non-rigid), and theassociated strain rate.

TABLE 3 Strain Rate Dogbone Type MaterialType (mm/min) IV Rigid 5 VRigid 1 IV Non-rigid 50 V Non-rigid 10Dogbone type IV is used to test elastomeric samples.

The samples were tested at a rate such that the sample ruptures at atime between 30 seconds to 5 minutes to ensure that sample strain rateis slow enough to capture plastic deformation in the samples.

Measured dogbone samples that do not rupture in the middle rectangularsection are excluded. Samples that break in the grips or prior totesting are not representative of the anticipated failure modes and areexcluded from the data.

Persuant to ASTM D-638, measure the Young's modulus (modulus ofelasticity) (slope of the stress-strain plot between 5-10% elongation),tensile strength at break, tensile strength at yield, percent elongationat break, percent elongation at yield.

A strain rate is chosen such that the part with the loweststrain-at-break (%) will fail within 5 minutes. This often means that aslower strain rate will be necessary for rigid samples.

Example 19 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Components as shown in Table 4, except PACM, were added to a containerand thoroughly mixed (either by an overhead stirrer or a centrifugationmixer such as THINKY™ mixer) to obtain a homogeneous resin. Then PACMwas added to the resin and mixed for another 2-30 min depending on thevolume and viscosity of resin. The resin was formed by CLIP as describedabove into D638 Type IV dog-bone-shaped specimens followed by thermalcuring at 125° C. for 2 h. The cured elastomer specimens were testedfollowing ASTM standard D638-10 on an Instron apparatus for mechanicalproperties as described above, which properties are also summarized inTable 4.

TABLE 4 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 697 DEGMA 82 IBMA123 PACM 83 PPO 5 Tensile Strength (MPa) 13.1 % Elongation at Break 395

Example 20 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example19 but using the formulation in Table 5. The cured specimens were testedfollowing ASTM standard on an Instron apparatus for mechanicalproperties as described above, which properties are summarized in Table5.

TABLE 5 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 721 DEGMA 84 IBMA126 PACM 54 PPO 5 Tensile Strength (MPa) 26.8 % Elongation at Break 515

Example 21 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example19 but using the formulation in Table 6. The cured specimens were testedfollowing ASTM standard on an Instron apparatus for mechanicalproperties as described above, which properties are summarized in Table6.

TABLE 6 Parts by weight ABPU(PTMO2k + HMDI + TBAEMA) 728 DEGMA 86 IBMA128 PACM 53 PPO 5 Tensile Strength (MPa) 23.1 % Elongation at Break 456

Example 22 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Components as shown in Table 7 were added to a container and thoroughlymixed (either by an overhead stirrer or a centrifugation mixer such asTHINKY™ mixer) to obtain a homogeneous resin. The resin was casted intoa square mold (with dimensions of 100×100×4 mm), and UV flood cured for1 min, followed by thermal curing at 125° C. for 2 h. The obtainedelastomer sheet was die-cut into rectangular bars with dimensions of100×20×4 mm. The elastomer specimens were tested following ASTM standardD638-10 on an Instron apparatus for mechanical properties as describedabove, which properties are summarized in Table 7.

TABLE 7 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 666 2-EHMA 131 IBMA66 MDEA 123 PPO 10 Tensile Strength (MPa) 14.4 % Elongation at Break 370

Example 23 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 8. The elastomer specimens weretested following ASTM standard D638-an Instron apparatus for mechanicalproperties as described above, which properties are summarized in Table8.

TABLE 8 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 692 DEGMA 102 2-EHMA102 PEGDMA 14 PACM 80 PPO 10 Tensile Strength (MPa) 6.42 % Elongation atBreak 388

Example 24 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 9. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 9.

TABLE 9 Parts by weight ABPU(PTMO1k + IPDI + TBAEMA) 700 DEGMA 206PEGDMA 10 PACM 74 PPO 10 Tensile Strength (MPa) 11.26 % Elongation atBreak 366

Example 25 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 10. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 10.

TABLE 10 Parts by weight ABPU(PTMO1k + MDI + TBAEMA) 672 2-EHMA 248PEGDMA 10 PACM 60 PPO 10 Tensile Strength (MPa) 24.93 % Elongation atBreak 320

Example 26 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 11. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 11.

TABLE 11 Parts by weight ABPU(PTMO1k + MDI + TBAEMA) 698 DEGMA 208PEGDMA 10 PACM 74 PPO 10 Tensile Strength (MPa) 20.14 % Elongation atBreak 355

Example 27 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 12. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 12.

TABLE 12 Parts by weight ABPU(PTMO2k + HMDI + TBAEMA) 2000 DEGMA 4002-EHMA 200 PEGDMA 66 PACM 145 PPO 14 Tensile Strength (MPa) 16.7 %Elongation at Break 476

Example 28 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 13. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 13.

TABLE 13 Parts by weight ABPU(PTMO2k + HMDI + TBAEMA) 2000 DEGMA 4002-EHMA 200 PACM 145 PPO 14 Tensile Strength (MPa) 16.9 % Elongation atBreak 499

Example 29 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 14 by mixing all the componentstogether. The elastomer specimens were tested following ASTM standardD638-10 on an Instron apparatus for mechanical properties as describedabove, which properties are summarized in Table 14.

TABLE 14 Parts by weight ABPU(PTMO2k + HMDI + TBAEMA) 2000 DEGMA 4002-EHMA 200 PEGDMA 66 BDO 62 PPO 14 Tensile Strength (MPa) 2.14 %Elongation at Break 188

Example 30 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 15. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 15.

TABLE 15 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2000 DEGMA 4202-EHMA 180 PEGDMA 67 PACM 149 PPO 14 Tensile Strength (MPa) 8.37 %Elongation at Break 386

Example 31 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 16. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 16.

TABLE 16 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2400 2-EHMA 700PACM 179 PPO 16 Tensile Strength (MPa) 17.2 % Elongation at Break 557

Example 32 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 17. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 17.

TABLE 17 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2400 2-EHMA 630PEGDMA 70 PACM 179 PPO 16 Tensile Strength (MPa) 13.4 % Elongation atBreak 520

Example 33 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 18. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 18.

TABLE 18 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2000 DEGMA 4002-EHMA 200 PACM 149 PPO 14 Tensile Strength (MPa) 13.6 % Elongation atBreak 529

Example 34 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 19. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 19.

TABLE 19 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2000 DEGMA 5002-EHMA 500 PACM 149 PPO 14 Tensile Strength (MPa) 9.32 % Elongation atBreak 485

Example 35 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 20. The elastomer specimens weretested following ASTM standard D638-10 on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 20.

TABLE 20 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2000 DEGMA 6502-EHMA 750 PACM 149 PPO 14 Tensile Strength (MPa) 5.14 % Elongation atBreak 440

Example 36 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 21. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 21.

TABLE 21 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 2000 DEGMA 580 PACM246 PPO 14 Tensile Strength (MPa) 6.48 % Elongation at Break 399

Example 37 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 22. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 22.

TABLE 22 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 2000 DEGMA 580PEGDMA 60 PACM 246 PPO 14 Tensile Strength (MPa) 6.49 % Elongation atBreak 353

Example 38 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 23. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 23.

TABLE 23 Parts by weight ABPU(PTMO1k + HDI + TBAEMA) 2000 DEGMA 6202-EHMA 180 PACM 246 PPO 14 Tensile Strength (MPa) 6.83 % Elongation atBreak 415

Example 39 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 24. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 24.

TABLE 24 Parts by weight ABPU(PTMO2k + HMDI + TBAEMA) 2000 DEGMA 4002-EHMA 200 PEGDMA 66 PACM 145 PPO 14 Tensile Strength (MPa) 15.6 %Elongation at Break 523

Example 40 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens were prepared in the same manner as in Example22 but using the formulation in Table 25. The elastomer specimens weretested following ASTM standard D638-on an Instron apparatus formechanical properties as described above, which properties aresummarized in Table 25.

TABLE 25 Parts by weight ABPU(PTMO2k + IPDI + TBAEMA) 2000 DEGMA 4202-EHMA 180 PEGDMA 67 PACM 149 PPO 14 Tensile Strength (MPa) 13.2 %Elongation at Break 480

Example 41 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Components as shown in Table 26, except PACM, were added to a containerand thoroughly mixed (either by an overhead stirrer or THINKY™ mixer) toobtain a homogeneous resin. Then PACM was added to the resin and mixedfor another 30 min. The resin was cast into dog-bone-shaped specimens byUV flood cure for 60 seconds followed by thermal curing at 125° C. for 4h. The cured specimens were tested following ASTM standard on an Instronapparatus for mechanical properties as described above, which propertiesare also summarized in Table 26.

TABLE 26 Component Weight % ABPU ABPU-1K-MDI 61.78 Reactive Diluent IBMA30.89 Chain Extender PACM 6.56 Initiator PPO 0.77 Tensile Strength (MPa)31.7 Modulus (MPa) 680 Elongation (%) 273

Example 42 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 27. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 27.

TABLE 27 Component Weight % ABPU ABPU-1K-MDI 53.51 Reactive Diluent IBMA40.13 Chain Extender PACM 5.69 Initiator PPO 0.67 Tensile Strength (MPa)26.2 Modulus (MPa) 1020 Elongation (%) 176

Example 43 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 28. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 28.

TABLE 28 Component Weight % ABPU ABPU-1K-MDI 47.2 Reactive Diluent IBMA47.2 Chain Extender PACM 5.01 Initiator PPO 0.59 Tensile Strength (MPa)29.5 Modulus (MPa) 1270 Elongation (%) 3.21

Example 44 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 29. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 29.

TABLE 29 Component Weight % ABPU ABPU-1K-MDI 42.22 Reactive Diluent IBMA52.77 Chain Extender PACM 4.49 Initiator PPO 0.53 Tensile Strength (MPa)19.3 Modulus (MPa) 1490 Elongation (%) 1.42

Example 45 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 30. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 30.

TABLE 30 Component Weight % ABPU ABPU-1K-MDI 61.13 Reactive Diluent IBMA30.57 Chain Extender PACM 7.54 Initiator PPO 0.76 Tensile Strength (MPa)19.3 Modulus (MPa) 1490 Elongation (%) 1.42

Example 46 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 31. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 31.

TABLE 31 Component Weight % ABPU ABPU-1K-MDI 61.55 Reactive Diluent IBMA30.78 Chain Extender PACM 6.9 Initiator PPO 0.77 Tensile Strength (MPa)34.1 Modulus (MPa) 713 Elongation (%) 269

Example 47 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 32. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 32.

TABLE 32 Component Weight % ABPU ABPU-1K-MDI 61.98 Reactive Diluent IBMA30.99 Chain Extender PACM 6.25 Initiator PPO 0.77 Tensile Strength (MPa)39.7 Modulus (MPa) 664 Elongation (%) 277

Example 48 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 33. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 33.

TABLE 33 Component Weight % ABPU ABPU-1K-MDI 63.75 Reactive Diluent IBMA31.87 Chain Extender PACM 3.59 Initiator PPO 0.8 Tensile Strength (MPa)21.3 Modulus (MPa) 265 Elongation (%) 207

Example 49 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 34. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 34.

TABLE 34 Component Weight % ABPU ABPU-1K-MDI 63.75 Reactive Diluent IBMA31.87 Chain Extender PACM 5.02 Initiator PPO 0.8 Tensile Strength (MPa)22.7 Modulus (MPa) 312 Elongation (%) 211

Example 50 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 35. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 35.

TABLE 35 Component Weight % ABPU ABPU-1K-MDI 63.75 Reactive Diluent IBMA31.87 Chain Extender PACM 5.71 Initiator PPO 0.8 Tensile Strength (MPa)28.4 Modulus (MPa) 407 Elongation (%) 222

Example 51 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 36. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 36.

TABLE 36 Component Weight % ABPU ABPU-1K-MDI 63.03 Reactive Diluent IBMA31.51 Chain Extender BAMN 4.67 Initiator PPO 0.79 Tensile Strength (MPa)25.1 Modulus (MPa) 155 Elongation (%) 297

Example 52 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 37. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 37.

TABLE 37 Component Weight % ABPU ABPU-1K-MDI 63.03 Reactive Diluent IBMA31.35 Chain Extender BAMN 5.2 Initiator PPO 0.79 Tensile Strength (MPa)21.7 Modulus (MPa) 214 Elongation (%) 291

Example 53 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 38. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 38.

TABLE 38 Component Weight % ABPU ABPU-650- 52.62 HMDI Reactive DiluentIBMA 39.47 Chain Extender PACM 7.26 Initiator PPO 0.66 Tensile Strength(MPa) 31.7 Modulus (MPa) 1460 Elongation (%) 3.65

Example 54 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 39. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 39.

TABLE 39 Component Weight % ABPU ABPU-650- 60.6 HMDI Reactive DiluentIBMA 30.29 Chain Extender PACM 8.36 Initiator PPO 0.76 Tensile Strength(MPa) 29.4 Modulus (MPa) 864 Elongation (%) 191

Example 55 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 40. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 40.

TABLE 40 Component Weight % ABPU ABPU-650- 30.53 HMDI ABPU ABPU-1K-MDI30.53 Reactive Diluent IBMA 30.53 Chain Extender PACM 7.63 Initiator PPO0.76 Tensile Strength (MPa) 29.1 Modulus (MPa) 492 Elongation (%) 220

Example 56 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 41. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 41.

TABLE 41 Component Weight % ABPU ABPU-650- 54.6 HMDI Reactive DiluentIBMA 27.6 Crosslinker DUDMA 9.9 Chain Extender PACM 7.1 Initiator PPO0.8 Tensile Strength (MPa) 59.3 Modulus (MPa) 1880 Elongation (%) 91

Example 57 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 42. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 42.

TABLE 42 Component Weight % ABPU ABPU-650- 54.6 HMDI Reactive DiluentIBMA 18.8 Reactive Diluent PEMA 18.8 Chain Extender PACM 7.1 InitiatorPPO 0.8 Tensile Strength (MPa) 32.5 Modulus (MPa) 1050 Elongation (%)178

Example 58 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 43. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 43.

TABLE 43 Component Weight % ABPU PTMO-1K-MDI 53.6 Reactive Diluent IBMA23.1 Reactive Diluent PEMA 7.1 Crosslinker DUDMA 9.7 Chain Extender PACM5.7 Initiator PPO 0.8 Tensile Strength (MPa) 43.8 Modulus (MPa) 1030Elongation (%) 135

Example 59 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 44. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 44.

TABLE 44 Component Weight % ABPU PTMO-650- 55.1 HMDI Reactive DiluentIBMA 33.1 Crosslinker BPADMA 3.7 Chain Extender PACM 7.2 Initiator PPO0.9 Tensile Strength (MPa) 33 Modulus (MPa) 1390 Elongation (%) 57

Example 60 Dual-Cure Material from Reactive Blocked PolyurethanePrepolymer

Cured specimens were prepared in the same manner as in Example 41 butusing the formulation in Table 45. The specimens were tested followingASTM standard D638-10 on an Instron apparatus for mechanical propertiesas described above, which properties are summarized in Table 45.

TABLE 45 Component Weight % ABPU PTMO-650- 52.6 HMDI Reactive DiluentIBMA 14.9 Reactive Diluent PEMA 5.0 Crosslinker SR239 19.9 ChainExtender PACM 6.9 Initiator PPO 0.8 Tensile Strength (MPa) 44.5 Modulus(MPa) 1520 Elongation (%) 12.4

Example 61 Elastomer from a Reactive Blocked Polyurethane Prepolymer

Cured elastomer specimens are prepared in the same manner as in Example20 but using the formulation in Table 46 below. The cure specimens giveelastomeric properties similar to those disclosed above.

TABLE 46 Parts by weight ABPU (PTMO2k + IPDI + NVF) 721 DEGMA 84Isobornyl acrylate 126 PACM 54 PPO 5

Example 62 A Flexible, “PVC-like” Photo-curable Polyurethane

This example describes dual cure polyurethane resins that producematerials and products having physical properties similar to that ofplasticized PVC.

The material is made by combining a part A with a part B, photo-curingthe mixture to solidify it's shape, and then baking it at a certaintemperature to access the desired final properties. Below is a sampleformulation:

WEIGHT REACTANT (g) % WT. PART A ABPU-25 22.4 48.20937% IBMA 5.612.08355% LMA 13.45 28.94714% TMPTMA 0.27  0.58260% TPO 0.594  1.27841%WIKOFF BLACK 0.12 0.258264% PART B PACM 4.03  8.67338%

ABPU-25: this component is an acrylate blocked polyurethane. It containsa mixture of two oligomers. One is a 650 Da diol, poly(tetramethyleneoxide) [PTMO-650] capped with methylene bis(4-cyclohexylisocyanate)[HMDI] that has been capped once more with 2-(tert-butylamino)ethylmethacrylate [TBAEMA]. The second oligomer is TBAEMA capped HMDI. Thefinal stoichiometric ratio of TBAEMA:HMDI:PTMO is 3.4:2.7:1.

IBMA: isobornyl methacrylate, reactive diluents.

LMA: lauryl methacrylate, reactive diluents.

TMPTMA: trimethylolpropane trimethacrylate, crosslinker.

TPO: diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, photo-initiator.

Wikoff Black: dispersion of black pigment.

PACM: 4,4′-methylenebiscyclohexylamine, chain extender.

Part A is synthesized by adding all of the individual components into acontainer and mixing until homogeneous. It is easiest to make a stocksolution using one of the reactive diluents (LMA for example) and thephotoinitiator, which is a powder. This stock solution can be added tothe ABPU and the other components and makes it easier to incorporate thephoto-initiator.

Part B can be added directly to part A in a 1:22 ratio by weight. Onceboth parts have been mixed thoroughly in an orbital or overhead mixerthe liquid resin can be photo-cured.

After photo-curing the solid part may be washed in a solution ofisopropyl alcohol or Green Power Chemical Rapid Rinse to clean thesurface of any un-cured material. The part may be dried by patting downwith a towel or with the use of compressed air.

After drying, the part should be placed onto a non-stick pan and placedinto an oven at 120 degrees Celsius for up to 4 hours. After baking thepart should be placed on a counter-top to cool down. Let the part sitout for at least 24 hours before use.

Example 63 Representative Polyurethane Products Produced from Dual-CureMaterials

Polymerizable materials as described in the examples, or detaileddescription, above (or variations thereof that will be apparent to thoseskilled in the art) provide products with a range of different elasticproperties. Examples of those ranges of properties, from rigid, throughsemi-rigid (rigid and flexible), to flexible, and to elastomeric.Particular types of products that can be made from such materialsinclude but are not limited to those given in Table 47 below. Theproducts may contain reacted photoinitiator fragments (remnants of thefirst cure forming the intermediate product) when produced by someembodiments of methods as described above. It will be appreciated thatthe properties may be further adjusted by inclusion of additionalmaterials such as fillers and/or dyes, as discussed above.

The properties of the product, as characterized by the columns set forthin Table 47, can be influenced in a variety of ways.

In general, increasing the amount of amount of hard segment in thepolymer as compared to soft segment in the polymer will favor theproduction of more rigid, or rigid and flexible, materials. In onespecific example, increasing the amount of TBAEMA will increase theamount of hard segment, and will favor the production of more rigid, orrigid and flexible, materials.

Blending the constituents of the polymerizable liquid to generate morephases (e.g., 2 or 3) in the final polymerized product will tend tofavor the production of more resilient final products. For example, insome embodiments, a blend that generates 1 phase in the product willfavor the production of a rigid, or rigid and flexible, material, whilea blend that generates three phases in the material will, in someembodiments, favor the production of a flexible or elastomeric product.

Washing of the intermediate, and choice of wash liquid, can be used toinfluence the properties of the product. For example, a wash liquid thatsolubilizes a chain extender in the intermediate product and extractschain extender from the intermediate may soften the material, and favorthe production of less rigid products.

Altering the ratio of constituents that participate in the first curingstep, as compared to the constituents that participate in the secondcuring step, may also be used to alter the properties of the resultingproduct.

The inclusion of a filler in the resin, and the choice of filler (e.g.,silica, tougheners such as core-shell rubbers, etc.) may be used tochange the properties of the final product.

TABLE 47 Polyurethane Products by Properties and Example Products² Rigidand Flexible (Semi- Rigid Rigid) Flexible Elastomeric Young's 800-3500300-2500 25-250 0.5-40 Modulus (MPa) Tensile 30-100 20-70  3-20 0.5-30Strength (MPa) % Elongation  1-100 40-300 or 600 100-175    50-1000 atBreak Phase(s) of 1 or 2   1 or 2 1, 2, or 3 2 or 3 material¹Non-limiting Fasteners; Structural Automotive Foot-ware soles, Exampleelectronic device elements; hinges interior parts heels, innersolesProducts housings; gears, including living (handles, and midsoles;propellers, and hinges; boat and dashboards, bushings and impellers;wheels, watercraft hulls etc.); toys; gaskets; cushions; mechanical anddecks; wheels; figurines, etc. electronic device device housings;bottles, jars and housings, etc. tools, etc. other containers; pipes,liquid tubes and connectors, etc. ¹The number of phases in the productmaterial corresponds directly to the number of peaks the materialexhibits by dynamic mechanical analysis, such as with a Seiko Exstar6000 dynamic mechanical analyzer. Where the material is a composite of amatrix polymer and a filler, the number of phases in this row refers tothe number of phases of the matrix polymer. ²In the table above, thefollowing general terms and phrases include the following non-limitingspecific examples: “Fastener” includes, but is not limited to, nuts,bolts, screws, expansion fasteners, clips, buckles, etc, “Electronicdevice housing” includes, but is not limited to, partial and completecell phone housings, tablet computer housings, personal computerhousings, electronic recorder and storage media housings, video monitorhousings, keyboard housings, etc., “Mechanical device housing” includes,but is not limited to, partial and complete gear housings, pumphousings, motor housings, etc. “Structural elements” as used hereinincludes, but is not limited to, shells, panels, rods, beams (e.g.,I-beams, U-beams, W-beams, cylindrical beams, channels, etc), struts,ties, etc., for applications including architectural and building, civilengineering, automotive and other transportation (e.g., automotive bodypanel, hood, chassis, frame, roof, bumper, etc.), etc. “Tools” includes,but is not limited to, impact tools such as hammers, drive tools such asscrewdrivers, grasping tools such as pliers, etc., including componentparts thereof (e.g., drive heads, jaws, and impact heads). “Toys”includes single unitary formed items or component parts thereof,examples of which include but are not limited to model vehicles(including airplanes, rockets, space ships, automobiles, trains), dollsand figurines (including human figurines, animal figurines, robotfigurines, fantasy creature figurines, etc.), etc., including compositesthereof and component parts thereof.

Example 64 Polyurethane Products Having Multiple Structural Segmentsand/or MultipleTensile Properties

In examples 18-61 are given materials for the formation of polyurethaneproducts having a variety of different tensile properties, ranging fromelastomeric, to semi-rigid, to flexible, as described in Example 62above.

Because the polyurethane polymer is formed by curing the intermediateproduct (e.g., by heating or microwave irradiating), the process offabricating the product may be paused or interrupted one or more times,to change the polymerizable liquid. While a fault line or plane may beformed in the intermediate by the interruption, if the subsequentpolymerizable liquid is, in its second cure material, reactive with thatof the first, then the two distinct structural segments of theintermediate will cross-react and covalently couple to one anotherduring the second cure (e.g., by heating or microwave irradiation).Thus, for example, any of the materials described in examples 19-60above may be sequentially changed to form a product having multipledistinct structural segments with different tensile properties, whilestill being a unitary product with the different segments covalentlycoupled to one another.

For example, a hinge can be formed, with the hinge comprising a rigidsegment, coupled to a second elastic segment, coupled to a third rigidsegment, by sequentially changing polymerizable liquids (e.g., fromamong those described in examples 19-60 above) during the formation ofthe three-dimensional intermediate.

A shock absorber or vibration dampener can be formed in like manner,with the second segment being either elastic or semi-rigid.

A unitary rigid funnel and flexible hose assembly can be formed in likemanner.

Sequential changing of the polymerizable liquid can be carried out witha multi-port, feed-through carrier, system, such as described in PCTApplication Publication No. WO 2015/126834, or, where the polymerizableliquid is supplied in a reservoir positioned above the build surface,providing the reservoir and build surface as interchangeable cartridgesthat can be changed out or swapped during a pause in fabrication.

Example 65 Silicone Rubber Product

Phenylbis(2 4 6-trimethylbenzoyl)phosphine oxide (PPO) is dissolved inisobornyl acrylate (IBA) with a THINKY™ mixer. Methacryloxypropylterminated polydimethylsiloxane (DMS-R31; Gelest Inc.) is added to thesolution, followed by addition of Sylgard Part A and Part B (CorningPDMS precursors), and then further mixed with a THINKY™ mixer to producea homogeneous solution. The solution is loaded into an apparatus asdescribed above and a three-dimensional intermediate is produced byultraviolet curing as described above. The three-dimensionalintermediate is then thermally cured at 100° C. for 12 hours to producethe final silicone rubber product. Parts by weight and tensileproperties are given in Table 33 below.

TABLE 33 Parts by weight DMS-R31 40 IBA 20 Sylgard 184Part A 40 Sylgard184 Part B 4 PPO 1 Tensile Strength (MPa) 1.3 % Elongation at Break 130

Example 66 Epoxy Dual Cure Product

10.018 g EpoxAcast 690 resin part A and 3.040 g part B were mixed on aTHINKY™ mixer. 3.484 g was then mixed with 3.013 g of RKP5-78-1, a65/22/13 mix of Sartomer CN9782/N-vinylpyrrolidone/diethyleneglycoldiacrylate to give a clear blend which was cured in a “dog bone” shapedsample mold (for tensile strength testing) for 2 minutes under a Dymaxultraviolet lamp to give a very elastic but weak dog bone sample.

A second sample, RKP11-10-1 contained 3.517 g of the above epoxy and3.508 g of RKP5-90-3 and 65/33/2/0.25 blend of SartomerCN2920/N-vinylcaprolactam/N-vinylpyrrolidone/PPO initiator curedsimilarly to give a very flexible dog bone. A third 1:1 sample made withRKP5-84-8 50/20/30/0.25 CN2920/CN9031/NVF/PPO did not cure completelyand was discarded.

Later, first samples of an epoxy/acrylate dual cure resins were made, asfollows:

-   -   Smooth-On EpoxAcure 690 is an EEW 190 epoxy (probably the        diglycidyl ether of bisphenol A) sold with a        diaminopropyleneglycol oligomer curing agent and offering a 5 hr        open time/24 hr room temperature cure.    -   This was blended 1:1 with three print formulations. Two samples        were good homogeneous blends that gave highly elastic, but very        weak dog bone samples on standard 2 minute UV cure.    -   Subsequent thermal cure of the samples at 84° C. for 5 hrs gave        reasonably strong and stiff, but flexible samples, in one case        with tenacious adhesion to the polystyrene petri dish on which        it was cured. Tensiles were in the modest 5-8 MPa range, less        than the base acrylate resins.

Later, RKP1-17-2D a 66/33/1 mix of CN2920/NVC/DPO initiator was blendedwith EpoxAcure 690 in a 1:1 ratio and 2:1 ratio

The 1:1 epoxy/acrylate dual cure formulation previously prepared failedto print in a CLIP apparatus as described above, at 100 or 60 mm/hr, buta 1:2 ratio gave a decent argyle pattern at 60 mm/hr. The Smooth-OnEpoxAcure 690/CN2920/NVC argyle was post-cured at room temperature to aclear, flexible, if tacky, sample. Dog bones were also prepared.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

We claim:
 1. A method of forming a three-dimensional object, comprising:(a) providing a carrier and a fill level, and optionally an opticallytransparent member having a build surface defining said fill level, saidcarrier and said fill level having a build region therebetween; (b)filling said build region with a polymerizable liquid, saidpolymerizable liquid comprising a mixture of (i) a light polymerizableliquid first component, and (ii) a second solidifiable component that isdifferent from said first component; (c) irradiating said build regionwith light to form a solid polymer scaffold from said first componentand also advancing said carrier away from said build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, said three-dimensional object and containing said secondsolidifiable component carried in said scaffold in unsolidified and/oruncured form, said polymerizable liquid further comprising a Lewis acidor an oxidizable tin salt in said polymerizable liquid in an amounteffective to accelerate the formation of said three-dimensionalintermediate during said irradiating; (d) optionally washing saidthree-dimensional intermediate; and (e) concurrently with or subsequentto said irradiating step, solidifying and/or curing said secondsolidifiable component in said three-dimensional intermediate to formsaid three-dimensional object, wherein said three-dimensional objectcomprises a polymer blend, interpenetrating polymer network,semi-interpenetrating polymer network, or sequential interpenetratingpolymer network formed from said first component and said secondsolidifiable component.
 2. The method of claim 1, wherein said secondsolidifiable component is solubilized in or suspended in said firstcomponent.
 3. The method of claim 1, wherein said three-dimensionalintermediate is collapsible or compressible.
 4. The method of claim 1,wherein said solidifying and/or curing step (e) is carried outsubsequent to said irradiating step (c) and is carried out by: (i)heating said second solidifiable component; (ii) irradiating said secondsolidifiable component with light at a wavelength different from that ofthe light in said irradiating step (c); (iii) contacting said secondsolidifiable component to water; and/or (iv) contacting said secondsolidifiable component to a catalyst.
 5. The method of claim 1, wherein:said second solidifiable component comprises precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, an epoxyresin, a cyanate ester resin, or a natural rubber; and said solidifyingand/or curing step (e) is carried out by heating.
 6. A method of forminga three-dimensional object, comprising: (a) providing a carrier and afill level, and optionally an optically transparent member having abuild surface defining said fill level, said carrier and said fill levelhaving a build region therebetween; (b) filling said build region with apolymerizable liquid, said polymerizable liquid comprising a mixture of(i) a light polymerizable liquid first component, and (ii) a secondsolidifiable component that is different from said first component; (c)irradiating said build region with light to form a solid polymerscaffold from said first component and also advancing said carrier awayfrom said build surface to form a three-dimensional intermediate havingthe same shape as, or a shape to be imparted to, said three-dimensionalobject and containing said second solidifiable component carried in saidscaffold in unsolidified and/or uncured form, said polymerizable liquidfurther comprising a Lewis acid or an oxidizable tin salt in saidpolymerizable liquid in an amount effective to accelerate the formationof said three-dimensional intermediate during said irradiating; (d)optionally washing said three-dimensional intermediate; and (e)concurrently with or subsequent to said irradiating step, solidifyingand/or curing said second solidifiable component in saidthree-dimensional intermediate to form said three-dimensional object,wherein: said solidifying and/or curing step (e) is carried outsubsequent to said irradiating step; and said solidifying and/or curingstep (e) is carried out under conditions in which said solid polymerscaffold degrades and forms a constituent necessary for thepolymerization of said second solidifiable component.
 7. A method offorming a three-dimensional object, comprising: (a) providing a carrierand a fill level, and optionally an optically transparent member havinga build surface defining said fill level, said carrier and said filllevel having a build region therebetween; (b) filling said build regionwith a polymerizable liquid, said polymerizable liquid comprising amixture of (i) a light polymerizable liquid first component, and (ii) asecond solidifiable component that is different from said firstcomponent; (c) irradiating said build region with light to form a solidpolymer scaffold from said first component and also advancing saidcarrier away from said build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to,said three-dimensional object and containing said second solidifiablecomponent carried in said scaffold in unsolidified and/or uncured form,said polymerizable liquid further comprising a Lewis acid or anoxidizable tin salt in said polymerizable liquid in an amount effectiveto accelerate the formation of said three-dimensional intermediateduring said irradiating; (d) optionally washing said three-dimensionalintermediate; and (e) concurrently with or subsequent to saidirradiating step, solidifying and/or curing said second solidifiablecomponent in said three-dimensional intermediate to form saidthree-dimensional object, said first component comprising monomersand/or prepolymers that can be polymerized by exposure to actinicradiation or light, and said second solidifiable component solidifiableon contacting to heat, water, water vapor, light at a differentwavelength than that at which said first component is polymerized,catalysts, evaporation of a solvent from the polymerizable liquid,exposure to microwave irradiation, or combinations thereof.
 8. Themethod of claim 7, said first component monomers and/or prepolymerscomprising reactive end groups selected from the group consisting ofacrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, vinyl ethers, and combinationsthereof.
 9. The method of claim 7, said second solidifiable componentcomprising monomers and/or prepolymers comprising reactive end groupsselected from the group consisting of: epoxy/amine, epoxy/hydroxyl,oxetane/amine, oxetane/alcohol, isocyanate/hydroxyl, isocyanate/amine,isocyanate/carboxylic acid, cyanate ester, anhydride/amine,amine/carboxylic acid, amine/ester, hydroxyl/carboxylic acid,hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H, Si—Cl/hydroxyl,Si—Cl/amine, hydroxyl/aldehyde, amine/aldehyde, hydroxymethyl oralkoxymethyl amide/alcohol, aminoplast, alkyne/azide, click chemistryreactive groups, alkene/sulfur, alkene/thiol, alkyne/thiol,hydroxyl/halide, isocyanate/water, Si—OH/hydroxyl, Si—OH/water,Si—OH/Si—H, Si—OH/Si—OH, perfluorovinyl, diene/dienophiles, olefinmetathesis polymerization groups, olefin polymerization groups forZiegler-Natta catalysis, and ring-opening polymerization groups andmixtures thereof.
 10. A three-dimensional object comprised of: (a) alight polymerized first component, and (b) a second solidified componentdifferent from said first component; said first component and/or secondsolidified component further comprising a Lewis acid or an oxidizabletin salt; said object optionally comprising a polymer blend formed fromsaid first component and said second solidified component, with saidpolymer blend comprising an interpenetrating polymer network, asemi-interpenetrating polymer network, or a sequential interpenetratingpolymer network; and further comprising: (c) a third solidifiedcomponent different from said first component and second solidifiedcomponent, with said object having at least a first structural segmentand a second structural segment covalently coupled to one another, saidfirst structural segment comprised of said second solidified component,said second structural segment comprised of said third solidifiedcomponent, and both said first and second structural segments comprisedof the same or different light polymerized first component.
 11. Theobject of claim 10, wherein said second solidified component comprises athermoplastic polymer.
 12. The object of claim 10, produced by a processcomprising: (a) providing a carrier and an optically transparent memberhaving a build surface, said carrier and said build surface defining abuild region therebetween; (b) filling said build region with apolymerizable liquid, said polymerizable liquid comprising a mixture of(i) a light polymerizable liquid first component, and (ii) a secondsolidifiable component different from said first component; (c)irradiating said build region with light through said opticallytransparent member to form a solid polymer scaffold from said firstcomponent and also advancing said carrier away from said build surfaceto form a three-dimensional intermediate having the same shape as, or ashape to be imparted to, said three-dimensional object and containingsaid second solidifiable component carried in said scaffold inunsolidified and/or uncured form; and (d) concurrently with orsubsequent to said irradiating step, solidifying and/or curing saidsecond solidifiable component in said three-dimensional intermediate toform said three-dimensional object.
 13. The object of claim 10, whereinsaid Lewis acid or oxidizable tin salt is included in an amount of from0.01 to 2 percent by weight.
 14. The object of claim 10, wherein saidoxidizable tin salt is stannous butanoate, stannous octoate, stannoushexanoate, stannous heptanoate, stannous linoleate, stannous phenylbutanoate, stannous phenyl stearate, stannous phenyl oleate, stannousnonanoate, stannous decanoate, stannous undecanoate, stannousdodecanoate, stannous stearate, stannous oleate stannous undecenoate,stannous 2-ethylhexoate, dibutyl tin dilaurate, dibutyl tin dioleate,dibutyl tin distearate, dipropyl tin dilaurate, dipropyl tin dioleate,dipropyl tin distearate, dibutyl tin dihexanoate, or a combinationthereof.
 15. The object of claim 10, wherein said oxidizable tin saltcomprises stannous octoate.
 16. A polymerizable liquid useful for theproduction of a three-dimensional object comprised of polyurethane,polyurea, or a copolymer thereof by additive manufacturing, saidpolymerizable liquid comprising a mixture of: (a) a blocked or reactiveblocked prepolymer, (b) a chain extender, (c) a photoinitiator, (d)optionally a polyol and/or a polyamine, (e) optionally a reactivediluent, (f) a light absorbing pigment or dye in an amount of from 0.001to 10 percent by weight, (g) optionally a filler, and (h) a Lewis acidor an oxidizable tin salt.
 17. The polymerizable liquid of claim 16,wherein said Lewis acid or oxidizable tin salt is included in an amountof from 0.01 to 2 percent by weight.
 18. The polymerizable liquid ofclaim 16, wherein said oxidizable tin salt is stannous butanoate,stannous octoate, stannous hexanoate, stannous heptanoate, stannouslinoleate, stannous phenyl butanoate, stannous phenyl stearate, stannousphenyl oleate, stannous nonanoate, stannous decanoate, stannousundecanoate, stannous dodecanoate, stannous stearate, stannous oleate,stannous undecenoate, stannous 2-ethylhexoate, dibutyl tin dilaurate,dibutyl tin dioleate, dibutyl tin distearate, dipropyl tin dilaurate,dipropyl tin dioleate, dipropyl tin distearate, dibutyl tin dihexanoate,or a combination thereof.
 19. The polymerizable liquid of claim 16,wherein said oxidizable tin salt comprises stannous octoate.